case study as a research method aims to

The Ultimate Guide to Qualitative Research - Part 1: The Basics

• Introduction and overview
• What is qualitative research?
• What is qualitative data?
• Examples of qualitative data
• Qualitative vs. quantitative research
• Mixed methods
• Qualitative research preparation
• Theoretical perspective
• Theoretical framework
• Literature reviews

Research question

• Conceptual framework
• Conceptual vs. theoretical framework

Data collection

• Qualitative research methods
• Focus groups
• Observational research

What is a case study?

Applications for case study research, what is a good case study, process of case study design, benefits and limitations of case studies.

• Ethnographical research
• Ethical considerations
• Confidentiality and privacy
• Power dynamics
• Reflexivity

Case studies

Case studies are essential to qualitative research , offering a lens through which researchers can investigate complex phenomena within their real-life contexts. This chapter explores the concept, purpose, applications, examples, and types of case studies and provides guidance on how to conduct case study research effectively.

Whereas quantitative methods look at phenomena at scale, case study research looks at a concept or phenomenon in considerable detail. While analyzing a single case can help understand one perspective regarding the object of research inquiry, analyzing multiple cases can help obtain a more holistic sense of the topic or issue. Let's provide a basic definition of a case study, then explore its characteristics and role in the qualitative research process.

Definition of a case study

A case study in qualitative research is a strategy of inquiry that involves an in-depth investigation of a phenomenon within its real-world context. It provides researchers with the opportunity to acquire an in-depth understanding of intricate details that might not be as apparent or accessible through other methods of research. The specific case or cases being studied can be a single person, group, or organization – demarcating what constitutes a relevant case worth studying depends on the researcher and their research question .

Among qualitative research methods , a case study relies on multiple sources of evidence, such as documents, artifacts, interviews , or observations , to present a complete and nuanced understanding of the phenomenon under investigation. The objective is to illuminate the readers' understanding of the phenomenon beyond its abstract statistical or theoretical explanations.

Characteristics of case studies

Case studies typically possess a number of distinct characteristics that set them apart from other research methods. These characteristics include a focus on holistic description and explanation, flexibility in the design and data collection methods, reliance on multiple sources of evidence, and emphasis on the context in which the phenomenon occurs.

Furthermore, case studies can often involve a longitudinal examination of the case, meaning they study the case over a period of time. These characteristics allow case studies to yield comprehensive, in-depth, and richly contextualized insights about the phenomenon of interest.

The role of case studies in research

Case studies hold a unique position in the broader landscape of research methods aimed at theory development. They are instrumental when the primary research interest is to gain an intensive, detailed understanding of a phenomenon in its real-life context.

In addition, case studies can serve different purposes within research - they can be used for exploratory, descriptive, or explanatory purposes, depending on the research question and objectives. This flexibility and depth make case studies a valuable tool in the toolkit of qualitative researchers.

Remember, a well-conducted case study can offer a rich, insightful contribution to both academic and practical knowledge through theory development or theory verification, thus enhancing our understanding of complex phenomena in their real-world contexts.

What is the purpose of a case study?

Case study research aims for a more comprehensive understanding of phenomena, requiring various research methods to gather information for qualitative analysis . Ultimately, a case study can allow the researcher to gain insight into a particular object of inquiry and develop a theoretical framework relevant to the research inquiry.

Why use case studies in qualitative research?

Using case studies as a research strategy depends mainly on the nature of the research question and the researcher's access to the data.

Conducting case study research provides a level of detail and contextual richness that other research methods might not offer. They are beneficial when there's a need to understand complex social phenomena within their natural contexts.

The explanatory, exploratory, and descriptive roles of case studies

Case studies can take on various roles depending on the research objectives. They can be exploratory when the research aims to discover new phenomena or define new research questions; they are descriptive when the objective is to depict a phenomenon within its context in a detailed manner; and they can be explanatory if the goal is to understand specific relationships within the studied context. Thus, the versatility of case studies allows researchers to approach their topic from different angles, offering multiple ways to uncover and interpret the data .

The impact of case studies on knowledge development

Case studies play a significant role in knowledge development across various disciplines. Analysis of cases provides an avenue for researchers to explore phenomena within their context based on the collected data.

This can result in the production of rich, practical insights that can be instrumental in both theory-building and practice. Case studies allow researchers to delve into the intricacies and complexities of real-life situations, uncovering insights that might otherwise remain hidden.

Types of case studies

In qualitative research , a case study is not a one-size-fits-all approach. Depending on the nature of the research question and the specific objectives of the study, researchers might choose to use different types of case studies. These types differ in their focus, methodology, and the level of detail they provide about the phenomenon under investigation.

Understanding these types is crucial for selecting the most appropriate approach for your research project and effectively achieving your research goals. Let's briefly look at the main types of case studies.

Exploratory case studies

Exploratory case studies are typically conducted to develop a theory or framework around an understudied phenomenon. They can also serve as a precursor to a larger-scale research project. Exploratory case studies are useful when a researcher wants to identify the key issues or questions which can spur more extensive study or be used to develop propositions for further research. These case studies are characterized by flexibility, allowing researchers to explore various aspects of a phenomenon as they emerge, which can also form the foundation for subsequent studies.

Descriptive case studies

Descriptive case studies aim to provide a complete and accurate representation of a phenomenon or event within its context. These case studies are often based on an established theoretical framework, which guides how data is collected and analyzed. The researcher is concerned with describing the phenomenon in detail, as it occurs naturally, without trying to influence or manipulate it.

Explanatory case studies

Explanatory case studies are focused on explanation - they seek to clarify how or why certain phenomena occur. Often used in complex, real-life situations, they can be particularly valuable in clarifying causal relationships among concepts and understanding the interplay between different factors within a specific context.

Intrinsic, instrumental, and collective case studies

These three categories of case studies focus on the nature and purpose of the study. An intrinsic case study is conducted when a researcher has an inherent interest in the case itself. Instrumental case studies are employed when the case is used to provide insight into a particular issue or phenomenon. A collective case study, on the other hand, involves studying multiple cases simultaneously to investigate some general phenomena.

Each type of case study serves a different purpose and has its own strengths and challenges. The selection of the type should be guided by the research question and objectives, as well as the context and constraints of the research.

The flexibility, depth, and contextual richness offered by case studies make this approach an excellent research method for various fields of study. They enable researchers to investigate real-world phenomena within their specific contexts, capturing nuances that other research methods might miss. Across numerous fields, case studies provide valuable insights into complex issues.

Critical information systems research

Case studies provide a detailed understanding of the role and impact of information systems in different contexts. They offer a platform to explore how information systems are designed, implemented, and used and how they interact with various social, economic, and political factors. Case studies in this field often focus on examining the intricate relationship between technology, organizational processes, and user behavior, helping to uncover insights that can inform better system design and implementation.

Health research

Health research is another field where case studies are highly valuable. They offer a way to explore patient experiences, healthcare delivery processes, and the impact of various interventions in a real-world context.

Case studies can provide a deep understanding of a patient's journey, giving insights into the intricacies of disease progression, treatment effects, and the psychosocial aspects of health and illness.

Asthma research studies

Specifically within medical research, studies on asthma often employ case studies to explore the individual and environmental factors that influence asthma development, management, and outcomes. A case study can provide rich, detailed data about individual patients' experiences, from the triggers and symptoms they experience to the effectiveness of various management strategies. This can be crucial for developing patient-centered asthma care approaches.

Other fields

Apart from the fields mentioned, case studies are also extensively used in business and management research, education research, and political sciences, among many others. They provide an opportunity to delve into the intricacies of real-world situations, allowing for a comprehensive understanding of various phenomena.

Case studies, with their depth and contextual focus, offer unique insights across these varied fields. They allow researchers to illuminate the complexities of real-life situations, contributing to both theory and practice.

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Understanding the key elements of case study design is crucial for conducting rigorous and impactful case study research. A well-structured design guides the researcher through the process, ensuring that the study is methodologically sound and its findings are reliable and valid. The main elements of case study design include the research question , propositions, units of analysis, and the logic linking the data to the propositions.

The research question is the foundation of any research study. A good research question guides the direction of the study and informs the selection of the case, the methods of collecting data, and the analysis techniques. A well-formulated research question in case study research is typically clear, focused, and complex enough to merit further detailed examination of the relevant case(s).

Propositions

Propositions, though not necessary in every case study, provide a direction by stating what we might expect to find in the data collected. They guide how data is collected and analyzed by helping researchers focus on specific aspects of the case. They are particularly important in explanatory case studies, which seek to understand the relationships among concepts within the studied phenomenon.

Units of analysis

The unit of analysis refers to the case, or the main entity or entities that are being analyzed in the study. In case study research, the unit of analysis can be an individual, a group, an organization, a decision, an event, or even a time period. It's crucial to clearly define the unit of analysis, as it shapes the qualitative data analysis process by allowing the researcher to analyze a particular case and synthesize analysis across multiple case studies to draw conclusions.

Argumentation

This refers to the inferential model that allows researchers to draw conclusions from the data. The researcher needs to ensure that there is a clear link between the data, the propositions (if any), and the conclusions drawn. This argumentation is what enables the researcher to make valid and credible inferences about the phenomenon under study.

Understanding and carefully considering these elements in the design phase of a case study can significantly enhance the quality of the research. It can help ensure that the study is methodologically sound and its findings contribute meaningful insights about the case.

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Conducting a case study involves several steps, from defining the research question and selecting the case to collecting and analyzing data . This section outlines these key stages, providing a practical guide on how to conduct case study research.

Defining the research question

The first step in case study research is defining a clear, focused research question. This question should guide the entire research process, from case selection to analysis. It's crucial to ensure that the research question is suitable for a case study approach. Typically, such questions are exploratory or descriptive in nature and focus on understanding a phenomenon within its real-life context.

Selecting and defining the case

The selection of the case should be based on the research question and the objectives of the study. It involves choosing a unique example or a set of examples that provide rich, in-depth data about the phenomenon under investigation. After selecting the case, it's crucial to define it clearly, setting the boundaries of the case, including the time period and the specific context.

Previous research can help guide the case study design. When considering a case study, an example of a case could be taken from previous case study research and used to define cases in a new research inquiry. Considering recently published examples can help understand how to select and define cases effectively.

Developing a detailed case study protocol

A case study protocol outlines the procedures and general rules to be followed during the case study. This includes the data collection methods to be used, the sources of data, and the procedures for analysis. Having a detailed case study protocol ensures consistency and reliability in the study.

The protocol should also consider how to work with the people involved in the research context to grant the research team access to collecting data. As mentioned in previous sections of this guide, establishing rapport is an essential component of qualitative research as it shapes the overall potential for collecting and analyzing data.

Collecting data

Gathering data in case study research often involves multiple sources of evidence, including documents, archival records, interviews, observations, and physical artifacts. This allows for a comprehensive understanding of the case. The process for gathering data should be systematic and carefully documented to ensure the reliability and validity of the study.

Analyzing and interpreting data

The next step is analyzing the data. This involves organizing the data , categorizing it into themes or patterns , and interpreting these patterns to answer the research question. The analysis might also involve comparing the findings with prior research or theoretical propositions.

Writing the case study report

The final step is writing the case study report . This should provide a detailed description of the case, the data, the analysis process, and the findings. The report should be clear, organized, and carefully written to ensure that the reader can understand the case and the conclusions drawn from it.

Each of these steps is crucial in ensuring that the case study research is rigorous, reliable, and provides valuable insights about the case.

The type, depth, and quality of data in your study can significantly influence the validity and utility of the study. In case study research, data is usually collected from multiple sources to provide a comprehensive and nuanced understanding of the case. This section will outline the various methods of collecting data used in case study research and discuss considerations for ensuring the quality of the data.

Interviews are a common method of gathering data in case study research. They can provide rich, in-depth data about the perspectives, experiences, and interpretations of the individuals involved in the case. Interviews can be structured , semi-structured , or unstructured , depending on the research question and the degree of flexibility needed.

Observations

Observations involve the researcher observing the case in its natural setting, providing first-hand information about the case and its context. Observations can provide data that might not be revealed in interviews or documents, such as non-verbal cues or contextual information.

Documents and artifacts

Documents and archival records provide a valuable source of data in case study research. They can include reports, letters, memos, meeting minutes, email correspondence, and various public and private documents related to the case.

These records can provide historical context, corroborate evidence from other sources, and offer insights into the case that might not be apparent from interviews or observations.

Physical artifacts refer to any physical evidence related to the case, such as tools, products, or physical environments. These artifacts can provide tangible insights into the case, complementing the data gathered from other sources.

Ensuring the quality of data collection

Determining the quality of data in case study research requires careful planning and execution. It's crucial to ensure that the data is reliable, accurate, and relevant to the research question. This involves selecting appropriate methods of collecting data, properly training interviewers or observers, and systematically recording and storing the data. It also includes considering ethical issues related to collecting and handling data, such as obtaining informed consent and ensuring the privacy and confidentiality of the participants.

Data analysis

Analyzing case study research involves making sense of the rich, detailed data to answer the research question. This process can be challenging due to the volume and complexity of case study data. However, a systematic and rigorous approach to analysis can ensure that the findings are credible and meaningful. This section outlines the main steps and considerations in analyzing data in case study research.

Organizing the data

The first step in the analysis is organizing the data. This involves sorting the data into manageable sections, often according to the data source or the theme. This step can also involve transcribing interviews, digitizing physical artifacts, or organizing observational data.

Categorizing and coding the data

Once the data is organized, the next step is to categorize or code the data. This involves identifying common themes, patterns, or concepts in the data and assigning codes to relevant data segments. Coding can be done manually or with the help of software tools, and in either case, qualitative analysis software can greatly facilitate the entire coding process. Coding helps to reduce the data to a set of themes or categories that can be more easily analyzed.

Identifying patterns and themes

After coding the data, the researcher looks for patterns or themes in the coded data. This involves comparing and contrasting the codes and looking for relationships or patterns among them. The identified patterns and themes should help answer the research question.

Interpreting the data

Once patterns and themes have been identified, the next step is to interpret these findings. This involves explaining what the patterns or themes mean in the context of the research question and the case. This interpretation should be grounded in the data, but it can also involve drawing on theoretical concepts or prior research.

Verification of the data

The last step in the analysis is verification. This involves checking the accuracy and consistency of the analysis process and confirming that the findings are supported by the data. This can involve re-checking the original data, checking the consistency of codes, or seeking feedback from research participants or peers.

Like any research method , case study research has its strengths and limitations. Researchers must be aware of these, as they can influence the design, conduct, and interpretation of the study.

Understanding the strengths and limitations of case study research can also guide researchers in deciding whether this approach is suitable for their research question . This section outlines some of the key strengths and limitations of case study research.

Benefits include the following:

• Rich, detailed data: One of the main strengths of case study research is that it can generate rich, detailed data about the case. This can provide a deep understanding of the case and its context, which can be valuable in exploring complex phenomena.
• Flexibility: Case study research is flexible in terms of design , data collection , and analysis . A sufficient degree of flexibility allows the researcher to adapt the study according to the case and the emerging findings.
• Real-world context: Case study research involves studying the case in its real-world context, which can provide valuable insights into the interplay between the case and its context.
• Multiple sources of evidence: Case study research often involves collecting data from multiple sources , which can enhance the robustness and validity of the findings.

On the other hand, researchers should consider the following limitations:

• Generalizability: A common criticism of case study research is that its findings might not be generalizable to other cases due to the specificity and uniqueness of each case.
• Time and resource intensive: Case study research can be time and resource intensive due to the depth of the investigation and the amount of collected data.
• Complexity of analysis: The rich, detailed data generated in case study research can make analyzing the data challenging.
• Subjectivity: Given the nature of case study research, there may be a higher degree of subjectivity in interpreting the data , so researchers need to reflect on this and transparently convey to audiences how the research was conducted.

Being aware of these strengths and limitations can help researchers design and conduct case study research effectively and interpret and report the findings appropriately.

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Home » Case Study – Methods, Examples and Guide

Case Study – Methods, Examples and Guide

Table of Contents

A case study is a research method that involves an in-depth examination and analysis of a particular phenomenon or case, such as an individual, organization, community, event, or situation.

It is a qualitative research approach that aims to provide a detailed and comprehensive understanding of the case being studied. Case studies typically involve multiple sources of data, including interviews, observations, documents, and artifacts, which are analyzed using various techniques, such as content analysis, thematic analysis, and grounded theory. The findings of a case study are often used to develop theories, inform policy or practice, or generate new research questions.

Types of Case Study

Types and Methods of Case Study are as follows:

Single-Case Study

A single-case study is an in-depth analysis of a single case. This type of case study is useful when the researcher wants to understand a specific phenomenon in detail.

For Example , A researcher might conduct a single-case study on a particular individual to understand their experiences with a particular health condition or a specific organization to explore their management practices. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of a single-case study are often used to generate new research questions, develop theories, or inform policy or practice.

Multiple-Case Study

A multiple-case study involves the analysis of several cases that are similar in nature. This type of case study is useful when the researcher wants to identify similarities and differences between the cases.

For Example, a researcher might conduct a multiple-case study on several companies to explore the factors that contribute to their success or failure. The researcher collects data from each case, compares and contrasts the findings, and uses various techniques to analyze the data, such as comparative analysis or pattern-matching. The findings of a multiple-case study can be used to develop theories, inform policy or practice, or generate new research questions.

Exploratory Case Study

An exploratory case study is used to explore a new or understudied phenomenon. This type of case study is useful when the researcher wants to generate hypotheses or theories about the phenomenon.

For Example, a researcher might conduct an exploratory case study on a new technology to understand its potential impact on society. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as grounded theory or content analysis. The findings of an exploratory case study can be used to generate new research questions, develop theories, or inform policy or practice.

Descriptive Case Study

A descriptive case study is used to describe a particular phenomenon in detail. This type of case study is useful when the researcher wants to provide a comprehensive account of the phenomenon.

For Example, a researcher might conduct a descriptive case study on a particular community to understand its social and economic characteristics. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of a descriptive case study can be used to inform policy or practice or generate new research questions.

Instrumental Case Study

An instrumental case study is used to understand a particular phenomenon that is instrumental in achieving a particular goal. This type of case study is useful when the researcher wants to understand the role of the phenomenon in achieving the goal.

For Example, a researcher might conduct an instrumental case study on a particular policy to understand its impact on achieving a particular goal, such as reducing poverty. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of an instrumental case study can be used to inform policy or practice or generate new research questions.

Case Study Data Collection Methods

Here are some common data collection methods for case studies:

Interviews involve asking questions to individuals who have knowledge or experience relevant to the case study. Interviews can be structured (where the same questions are asked to all participants) or unstructured (where the interviewer follows up on the responses with further questions). Interviews can be conducted in person, over the phone, or through video conferencing.

Observations

Observations involve watching and recording the behavior and activities of individuals or groups relevant to the case study. Observations can be participant (where the researcher actively participates in the activities) or non-participant (where the researcher observes from a distance). Observations can be recorded using notes, audio or video recordings, or photographs.

Documents can be used as a source of information for case studies. Documents can include reports, memos, emails, letters, and other written materials related to the case study. Documents can be collected from the case study participants or from public sources.

Surveys involve asking a set of questions to a sample of individuals relevant to the case study. Surveys can be administered in person, over the phone, through mail or email, or online. Surveys can be used to gather information on attitudes, opinions, or behaviors related to the case study.

Artifacts are physical objects relevant to the case study. Artifacts can include tools, equipment, products, or other objects that provide insights into the case study phenomenon.

How to conduct Case Study Research

Conducting a case study research involves several steps that need to be followed to ensure the quality and rigor of the study. Here are the steps to conduct case study research:

• Define the research questions: The first step in conducting a case study research is to define the research questions. The research questions should be specific, measurable, and relevant to the case study phenomenon under investigation.
• Select the case: The next step is to select the case or cases to be studied. The case should be relevant to the research questions and should provide rich and diverse data that can be used to answer the research questions.
• Collect data: Data can be collected using various methods, such as interviews, observations, documents, surveys, and artifacts. The data collection method should be selected based on the research questions and the nature of the case study phenomenon.
• Analyze the data: The data collected from the case study should be analyzed using various techniques, such as content analysis, thematic analysis, or grounded theory. The analysis should be guided by the research questions and should aim to provide insights and conclusions relevant to the research questions.
• Draw conclusions: The conclusions drawn from the case study should be based on the data analysis and should be relevant to the research questions. The conclusions should be supported by evidence and should be clearly stated.
• Validate the findings: The findings of the case study should be validated by reviewing the data and the analysis with participants or other experts in the field. This helps to ensure the validity and reliability of the findings.
• Write the report: The final step is to write the report of the case study research. The report should provide a clear description of the case study phenomenon, the research questions, the data collection methods, the data analysis, the findings, and the conclusions. The report should be written in a clear and concise manner and should follow the guidelines for academic writing.

Examples of Case Study

Here are some examples of case study research:

• The Hawthorne Studies : Conducted between 1924 and 1932, the Hawthorne Studies were a series of case studies conducted by Elton Mayo and his colleagues to examine the impact of work environment on employee productivity. The studies were conducted at the Hawthorne Works plant of the Western Electric Company in Chicago and included interviews, observations, and experiments.
• The Stanford Prison Experiment: Conducted in 1971, the Stanford Prison Experiment was a case study conducted by Philip Zimbardo to examine the psychological effects of power and authority. The study involved simulating a prison environment and assigning participants to the role of guards or prisoners. The study was controversial due to the ethical issues it raised.
• The Challenger Disaster: The Challenger Disaster was a case study conducted to examine the causes of the Space Shuttle Challenger explosion in 1986. The study included interviews, observations, and analysis of data to identify the technical, organizational, and cultural factors that contributed to the disaster.
• The Enron Scandal: The Enron Scandal was a case study conducted to examine the causes of the Enron Corporation’s bankruptcy in 2001. The study included interviews, analysis of financial data, and review of documents to identify the accounting practices, corporate culture, and ethical issues that led to the company’s downfall.
• The Fukushima Nuclear Disaster : The Fukushima Nuclear Disaster was a case study conducted to examine the causes of the nuclear accident that occurred at the Fukushima Daiichi Nuclear Power Plant in Japan in 2011. The study included interviews, analysis of data, and review of documents to identify the technical, organizational, and cultural factors that contributed to the disaster.

Application of Case Study

Case studies have a wide range of applications across various fields and industries. Here are some examples:

Business and Management

Case studies are widely used in business and management to examine real-life situations and develop problem-solving skills. Case studies can help students and professionals to develop a deep understanding of business concepts, theories, and best practices.

Case studies are used in healthcare to examine patient care, treatment options, and outcomes. Case studies can help healthcare professionals to develop critical thinking skills, diagnose complex medical conditions, and develop effective treatment plans.

Case studies are used in education to examine teaching and learning practices. Case studies can help educators to develop effective teaching strategies, evaluate student progress, and identify areas for improvement.

Social Sciences

Case studies are widely used in social sciences to examine human behavior, social phenomena, and cultural practices. Case studies can help researchers to develop theories, test hypotheses, and gain insights into complex social issues.

Law and Ethics

Case studies are used in law and ethics to examine legal and ethical dilemmas. Case studies can help lawyers, policymakers, and ethical professionals to develop critical thinking skills, analyze complex cases, and make informed decisions.

Purpose of Case Study

The purpose of a case study is to provide a detailed analysis of a specific phenomenon, issue, or problem in its real-life context. A case study is a qualitative research method that involves the in-depth exploration and analysis of a particular case, which can be an individual, group, organization, event, or community.

The primary purpose of a case study is to generate a comprehensive and nuanced understanding of the case, including its history, context, and dynamics. Case studies can help researchers to identify and examine the underlying factors, processes, and mechanisms that contribute to the case and its outcomes. This can help to develop a more accurate and detailed understanding of the case, which can inform future research, practice, or policy.

Case studies can also serve other purposes, including:

• Illustrating a theory or concept: Case studies can be used to illustrate and explain theoretical concepts and frameworks, providing concrete examples of how they can be applied in real-life situations.
• Developing hypotheses: Case studies can help to generate hypotheses about the causal relationships between different factors and outcomes, which can be tested through further research.
• Providing insight into complex issues: Case studies can provide insights into complex and multifaceted issues, which may be difficult to understand through other research methods.
• Informing practice or policy: Case studies can be used to inform practice or policy by identifying best practices, lessons learned, or areas for improvement.

Advantages of Case Study Research

There are several advantages of case study research, including:

• In-depth exploration: Case study research allows for a detailed exploration and analysis of a specific phenomenon, issue, or problem in its real-life context. This can provide a comprehensive understanding of the case and its dynamics, which may not be possible through other research methods.
• Rich data: Case study research can generate rich and detailed data, including qualitative data such as interviews, observations, and documents. This can provide a nuanced understanding of the case and its complexity.
• Holistic perspective: Case study research allows for a holistic perspective of the case, taking into account the various factors, processes, and mechanisms that contribute to the case and its outcomes. This can help to develop a more accurate and comprehensive understanding of the case.
• Theory development: Case study research can help to develop and refine theories and concepts by providing empirical evidence and concrete examples of how they can be applied in real-life situations.
• Practical application: Case study research can inform practice or policy by identifying best practices, lessons learned, or areas for improvement.
• Contextualization: Case study research takes into account the specific context in which the case is situated, which can help to understand how the case is influenced by the social, cultural, and historical factors of its environment.

Limitations of Case Study Research

There are several limitations of case study research, including:

• Limited generalizability : Case studies are typically focused on a single case or a small number of cases, which limits the generalizability of the findings. The unique characteristics of the case may not be applicable to other contexts or populations, which may limit the external validity of the research.
• Biased sampling: Case studies may rely on purposive or convenience sampling, which can introduce bias into the sample selection process. This may limit the representativeness of the sample and the generalizability of the findings.
• Subjectivity: Case studies rely on the interpretation of the researcher, which can introduce subjectivity into the analysis. The researcher’s own biases, assumptions, and perspectives may influence the findings, which may limit the objectivity of the research.
• Limited control: Case studies are typically conducted in naturalistic settings, which limits the control that the researcher has over the environment and the variables being studied. This may limit the ability to establish causal relationships between variables.
• Time-consuming: Case studies can be time-consuming to conduct, as they typically involve a detailed exploration and analysis of a specific case. This may limit the feasibility of conducting multiple case studies or conducting case studies in a timely manner.
• Resource-intensive: Case studies may require significant resources, including time, funding, and expertise. This may limit the ability of researchers to conduct case studies in resource-constrained settings.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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22 Case Study Research: In-Depth Understanding in Context

Helen Simons, School of Education, University of Southampton

• Published: 01 July 2014
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This chapter explores case study as a major approach to research and evaluation. After first noting various contexts in which case studies are commonly used, the chapter focuses on case study research directly Strengths and potential problematic issues are outlined and then key phases of the process. The chapter emphasizes how important it is to design the case, to collect and interpret data in ways that highlight the qualitative, to have an ethical practice that values multiple perspectives and political interests, and to report creatively to facilitate use in policy making and practice. Finally, it explores how to generalize from the single case. Concluding questions center on the need to think more imaginatively about design and the range of methods and forms of reporting requiredto persuade audiences to value qualitative ways of knowing in case study research.

Introduction

This chapter explores case study as a major approach to research and evaluation using primarily qualitative methods, as well as documentary sources, contemporaneous or historical. However, this is not the only way in which case study can be conceived. No one has a monopoly on the term. While sharing a focus on the singular in a particular context, case study has a wide variety of uses, not all associated with research. A case study, in common parlance, documents a particular situation or event in detail in a specific sociopolitical context. The particular can be a person, a classroom, an institution, a program, or a policy. Below I identify different ways in which case study is used before focusing on qualitative case study research in particular. However, first I wish to indicate how I came to advocate and practice this form of research. Origins, context, and opportunity often shape the research processes we endorse. It is helpful for the reader, I think, to know how I came to the perspective I hold.

The Beginnings

I first came to appreciate and enjoy the virtues of case study research when I entered the field of curriculum evaluation and research in the 1970s. The dominant research paradigm for educational research at that time was experimental or quasi- experimental, cost-benefit, or systems analysis, and the dominant curriculum model was aims and objectives ( House, 1993 ). The field was dominated, in effect, by a psychometric view of research in which quantitative methods were preeminent. But the innovative projects we were asked to evaluate (predominantly, but not exclusively, in the humanities) were not amenable to such methodologies. The projects were challenging to the status quo of institutions, involved people interpreting the policy and programs, were implemented differently in different contexts and regions, and had many unexpected effects.

We had no choice but to seek other ways to evaluate these complex programs, and case study was the methodology we found ourselves exploring, in order to understand how the projects were being implemented, why they had positive effects in some regions of the country and not others, and what the outcomes meant in different sociopolitical and cultural contexts. What better way to do this than to talk with people to see how they interpreted the “new” curriculum; to watch how teachers and students put it into practice; to document transactions, outcomes, and unexpected consequences; and to interpret all in the specific context of the case ( Simons, 1971 , 1987 , pp. 55–89). From this point on and in further studies, case study in educational research and evaluation came to be a major methodology for understanding complex educational and social programs. It also extended to other practice professions, such as nursing, health, and social care ( Zucker, 2001 ; Greenhalgh & Worrall, 1997 ; Shaw & Gould, 2001 ). For further details of the evolution of the case study approach and qualitative methodologies in evaluation, see House, 1993 , pp. 2–3; Greene, 2000 ; Simons, 2009 , pp. 14–18; Simons & McCormack, 2007 , pp. 292–311).

This was not exactly the beginning of case study, of course. It has a long history in many disciplines ( Simons, 1980; Ragin, 1992; Gomm, Hammersley, & Foster, 2004 ; Platt, 2007 ), many aspects of which form part of case study practice to this day. But its evolution in the context just described was a major move in the contemporary evolution of the logic of evaluative inquiry ( House, 1980 ). It also coincided with movement toward the qualitative in other disciplines, such as sociology and psychology. This was all part of what Denzin & Lincoln (1994) termed “a quiet methodological revolution” (p. ix) in qualitative inquiry that had been evolving over the course of forty years.

There is a further reason why I continue to advocate and practice case study research and evaluation to this day and that is my personal predilection for trying to understand and represent complexity, for puzzling through the ambiguities that exist in many contexts and programs and for presenting and negotiating different values and interests in fair and just ways.

Put more simply, I like interacting with people, listening to their stories, trials and tribulations—giving them a voice in understanding the contexts and projects with which they are involved, and finding ways to share these with a range of audiences. In other words, the move toward case study methodology described here suited my preference for how I learn.

Concepts and Purposes of Case Study

Before exploring case study as it has come to be established in educational research and evaluation over the past forty years, I wish to acknowledge other uses of case study. More often than not, these relate to purpose, and appropriately so in their different contexts, but many do not have a research intention. For a study to count as research, it would need to be a systematic investigation generating evidence that leads to “new” knowledge that is made public and open to scrutiny. There are many ways to conduct research stemming from different traditions and disciplines, but they all, in different ways, involve these characteristics.

Everyday Usage: Stories We Tell

The most common of these uses of case study is the everyday reference to a person, an anecdote or story illustrative of a particular incident, event, or experience of that person. It is often a short, reported account commonly seen in journalism but also in books exploring a phenomenon, such as recovery from serious accidents or tragedies, where the author chooses to illustrate the story or argument with a “lived” example. This is sometimes written by the author and sometimes by the person whose tale it is. “Let me share with you a story,” is a phrase frequently heard

The spirit behind this common usage and its power to connect can be seen in a report by Tim Adams of the London Olympics opening ceremony’s dramatization by Danny Boyle.

It was the point when we suddenly collectively wised up to the idea that what we are about to receive over the next two weeks was not only about “legacy collateral” and “targeted deliverables,” not about G4S failings and traffic lanes and branding opportunities, but about the second-by-second possibilities of human endeavour and spirit and communality, enacted in multiple places and all at the same time. Stories in other words. ( Adams, 2012 )

This was a collective story, of course, not an individual one, but it does convey some of the major characteristics of case study—that richness of detail, time, place, multiple happenings and experiences—that are also manifest in case study research, although carefully evidenced in the latter instance. We can see from this common usage how people have come to associate case study with story. I return to this thread in the reporting section.

Professions Individual Cases

In professional settings, in health and social care, case studies, often called case histories , are used to accurately record a person’s health or social care history and his or her current symptoms, experience, and treatment. These case histories include facts but also judgments and observations about the person’s reaction to situations or medication. Usually these are confidential. Not dissimilar is the detailed documentation of a case in law, often termed a case precedent when referred to in a court case to support an argument being made. However in law there is a difference in that such case precedents are publicly documented.

Case Studies in Teaching

Exemplars of practice.

In education, but also in health and social care training contexts, case studies have long been used as exemplars of practice. These are brief descriptions with some detail of a person or project’s experience in an area of practice. Though frequently reported accounts, they are based on a person’s experience and sometimes on previous research.

Case scenarios

Management studies are a further context in which case studies are often used. Here, the case is more like a scenario outlining a particular problem situation for the management student to resolve. These scenarios may be based on research but frequently are hypothetical situations used to raise issues for discussion and resolution. What distinguishes these case scenarios and the case exemplars in education from case study research is the intention to use them for teaching purposes.

Country Case Studies

Then there are case studies of programs, projects, and even countries, as in international development, where a whole-country study might be termed a case study or, in the context of the Organization for Economic Co-operation and Development (OECD), where an exploration is conducted of the state of the art of a subject, such as education or environmental science in one or several countries. This may be a contemporaneous study and/or what transpired in a program over a period of time. Such studies often do have a research base but frequently are reported accounts that do not detail the design, methodology, and analysis of the case, as a research case study would do, or report in ways that give readers a vicarious experience of what it was like to be there. Such case studies tend to be more knowledge and information-focused than experiential.

Case Study as History

Closer to a research context is case study as history—what transpired at a certain time in a certain place. This is likely to be supported by documentary evidence but not primary data gathering unless it is an oral history. In education, in the late 1970s, Stenhouse (1978) experimented with a case study archive. Using contemporaneous data gathering, primarily through interviewing, he envisaged this database, which he termed a “case record,” forming an archive from which different individuals,, at some later date, could write a “case study.” This approach uses case study as a documentary source to begin to generate a history of education, as the subtitle of Stenhouse’s 1978 paper indicates “Towards a contemporary history of education.”

Case Study Research

From here on, my focus is on case study research per se, adopting for this purpose the following definition:

Case study is an in-depth exploration from multiple perspectives of the complexity and uniqueness of a particular project, policy, institution or system in a “real-life” context. It is research based, inclusive of different methods and is evidence-led. ( Simons, 2009 , p. 21).

For further related definitions of case study, see Stake (1995) , Merriam (1998), and Chadderton & Torrance (2011) . And for definitions from a slightly different perspective, see Yin (2004) and Thomas (2011a) .

Not Defined by Method or Perspective

The inclusion of different methods in the definition quoted above definition signals that case study research is not defined by methodology or method. What defines case study is its singularity and the concept and boundary of the case. It is theoretically possible to conduct a case study using primarily quantitative data if this is the best way of providing evidence to inform the issues the case is exploring. It is equally possible to conduct case study that is mainly qualitative, to engage people with the experience of the case or to provide a rich portrayal of an event, project, or program.

Or one can design the case using mixed methods. This increases the options for learning from different ways of knowing and is sometimes preferred by stakeholders who believe it provides a firmer basis for informing policy. This is not necessarily the case but is beyond the scope of this chapter to explore. For further discussion of the complexities of mixing methods and the virtue of using qualitative methods and case study in a mixed method design, see Greene (2007) .

Case study research may also be conducted from different standpoints—realist, interpretivist, or constructivist, for example. My perspective falls within a constructivist, interpretivist framework. What interests me is how I and those in the case perceive and interpret what we find and how we construct or co-construct understandings of the case. This not only suits my predilection for how I see the world, but also my preferred phenomenological approach to interviewing and curiosity about people and how they act in social and professional life.

Qualitative Case Study Research

Qualitative case study research shares many characteristics with other forms of qualitative research, such as narrative, oral history, life history, ethnography, in-depth interview, and observational studies that utilize qualitative methods. However, its focus, purpose, and origins, in educational research at least, are a little different.

The focus is clearly the study of the singular. The purpose is to portray an in-depth view of the quality and complexity of social/educational programs or policies as they are implemented in specific sociopolitical contexts. What makes it qualitative is its emphasis on subjective ways of knowing, particularly the experiential, practical, and presentational rather than the propositional ( Heron, 1992 , 1999 ) to comprehend and communicate what transpired in the case.

Characteristic Features and Advantages

Case study research is not method dependent, as noted earlier, nor is it constrained by resources or time. Although it can be conducted over several years, which provides an opportunity to explore the process of change and explain how and why things happened, it can equally be carried out contemporaneously in a few days, weeks, or months. This flexibility is extremely useful in many contexts, particularly when a change in policy or unforeseen issues in the field require modifying the design.

Flexibility extends to reporting. The case can be written up in different lengths and forms to meet different audience needs and to maximize use (see the section on Reporting). Using the natural language of participants and familiar methods (like interview, observation, oral history) also enables participants to engage in the research process, thereby contributing significantly to the generation of knowledge of the case. As I have indicated elsewhere ( Simons, 2009 ), “This is both a political and epistemological point. It signals a potential shift in the power base of who controls knowledge and recognizes the importance of co-constructing perceived reality through the relationships and joint understandings we create in the field” (p. 23).

Possible Disadvantages

If one is an advocate, identifying advantages of a research approach is easier than pointing out its disadvantages, something detractors are quite keen to do anyway! But no approach is perfect, and here are some of the issues that often trouble people about case study research. The “sample of one” is an obvious issue that worries those convinced that only large samples can constitute valid research and especially if this is to inform policy. Understanding complexity in depth may not be a sufficient counterargument, and I suspect there is little point in trying to persuade otherwise For frequently, this perception is one of epistemological and methodological, if not ideological, preference.

However, there are some genuine concerns that many case researchers face: the difficulty of processing a mass of data; of “telling the truth” in contexts where people may be identifiable; personal involvement, when the researcher is the main instrument of data gathering; and writing reports that are data-based, yet readable in style and length. But one issue that concerns advocates and nonadvocates alike is how inferences are drawn from the single case.

Answers to some of these issues are covered in the sections that follow. Whether they convince may again be a question of preference. However, it is worth noting here that I do not think we should seek to justify these concerns in terms identified by other methodologies. Many of them are intrinsic to the nature and strength of qualitative case study research.

Subjectivity, for instance, both of participants and researcher is inevitable, as it is in many other qualitative methodologies. This is often the basis on which we act. Rather than see this as bias or something to counter, it is an intelligence that is essential to understanding and interpreting the experience of participants and stakeholders. Such subjectivity needs to be disciplined, of course, through procedures that examine both the validity of individuals’ representations of “their truth”, and demonstrate how the researcher took a reflexive approach to monitoring how his or her own values and predilections may have unduly influenced the data.

Types of Case Study

There are numerous types of case study, too many to categorize, I think, as there are overlaps between them. However, attempts have been made to do this and, for those who value typologies, I refer them to Bassey (1999) and, for a more extended typology, to Thomas (2011b) . A slightly different approach is taken by Gomm, Hammersley, and Foster (2004) in annotating the different emphases in major texts on case study. What I prefer to do here is to highlight a few familiar types to focus the discussion that follows on the practice of case study research.

Stake (1995) offers a threefold distinction that is helpful when it comes to practice, he says, because it influences the methods we choose to gather data (p. 4). He distinguishes between an intrinsic case study , one that is studied to learn about the particular case itself and an instrumental case study , in which we choose a case to gain insight into a particular issue (i.e., the case is instrumental to understanding something else; p. 3). The collective case study is what its name suggests: an extension of the instrumental to several cases.

Theory-led or theory-generated case study is similarly self-explanatory, the first starting from a specific theory that is tested through the case; the second constructing a theory through interpretation of data generated in the case. In other words, one ends rather than begins with a theory. In qualitative case study research, this is the more familiar route. The theory of the case becomes the argument or story you will tell.

Evaluation case study requires a slightly longer description as this is my context of practice, one which has influenced the way I conduct case study and what I choose to emphasize in this chapter. An evaluation case study has three essential features: to determine the value of the case, to include and balance different interests and values, and to report findings to a range of stakeholders in ways that they can use. The reasons for this may be found in the interlude that follows, which offers a brief characterization of the social and ethical practice of evaluation and why qualitative methods are so important in this practice.

Interlude: Social and Ethical Practice of Evaluation

Evaluation is a social practice that documents, portrays, and seeks to understand the value of a particular project, program, or policy. This can be determined by different evaluation methodologies, of course. But the value of qualitative case study is that it is possible to discern this value without decontextualizing the data. While the focus of the case is usually a project, program, policy, or some unit within, studies of key individuals, what I term case profiles , may be embedded within the overall case. In some instances, these profiles, or even shorter cameos of individuals, may be quite prominent. For it is through the perceptions, interpretations, and interactions of people that we learn how policies and programs are enacted ( Kushner, 2000 , p. 12). The program is still the main focus of analysis, but, in exploring how individuals play out their different roles in the program, we get closer to the actual experience and meaning of the program in practice.

Case study evaluation is often commissioned from an external source (government department or other agency) keen to know the worth of publicly funded programs and policies to inform future decision making. It needs to be responsive to issues or questions identified by stakeholders, who often have different values and interests in the expected outcomes and appreciate different perspectives of the program in action. The context also is often highly politicized, and interests can conflict. The task of the evaluator in such situations becomes one of including and balancing all interests and values in the program fairly and justly.

This is an inherently political process and requires an ethical practice that offers participants some protection over the personal data they give as part of the research and agreed audiences access to the findings, presented in ways they can understand. Negotiating what information becomes public can be quite difficult in singular settings where people are identifiable and intricate or problematic transactions have been documented. The consequences that ensue from making knowledge public that hitherto was private may be considerable for those in the case. It may also be difficult to portray some of the contextual detail that would enhance understanding for readers.

The ethical stance that underpins the case study research and evaluation I conduct stems from a theory of ethics that emphasizes the centrality of relationships in the specific context and the consequences for individuals, while remaining aware of the research imperative to publicly report. It is essentially an independent democratic process based on the concepts of fairness and justice, in which confidentiality, negotiation, and accessibility are key principles ( MacDonald, 1976 ; Simons, 2009 , pp. 96–111; and Simons 2010 ). The principles are translated into specific procedures to guide the collection, validation, and dissemination of data in the field. These include:

engaging participants and stakeholders in identifying issues to explore and sometimes also in interpreting the data;

documenting how different people interpret and value the program;

negotiating what data becomes public respecting both the individual’s “right to privacy” and the public’s “right to know”;

offering participants opportunities to check how their data are used in the context of reporting;

reporting in language and forms accessible to a wide range of audiences;

disseminating to audiences within and beyond the case.

For further discussion of the ethics of democratic case study evaluation and examples of their use in practice, see Simons (2000 , 2006 , 2009 , chapter 6, 2010 ).

Designing Case Study Research

Design issues in case study sometimes take second place to those of data gathering, the more exciting task perhaps in starting research. However, it is critical to consider the design at the outset, even if changes are required in practice due to the reality of what is encountered in the field. In this sense, the design of case study is emergent, rather than preordinate, shaped and reshaped as understanding of the significance of foreshadowed issues emerges and more are discovered.

Before entering the field, there are a myriad of planning issues to think about related to stakeholders, participants, and audiences. These include whose values matter, whether to engage them in data gathering and interpretation, the style of reporting appropriate for each, and the ethical guidelines that will underpin data collection and reporting. However, here I emphasize only three: the broad focus of the study, what the case is a case of, and framing questions/issues. These are steps often ignored in an enthusiasm to gather data, resulting in a case study that claims to be research but lacks the basic principles required for generation of valid, public knowledge.

Conceptualize the Topic

First, it is important that the topic of the research is conceptualized in a way that it can be researched (i.e., it is not too wide). This seems an obvious point to make, but failure to think through precisely what it is about your research topic you wish to investigate will have a knock-on effect on the framing of the case, data gathering, and interpretation and may lead, in some instances, to not gathering or analyzing data that actually informs the topic. Further conceptualization or reconceptualization may be necessary as the study proceeds, but it is critical to have a clear focus at the outset.

What Constitutes the Case

Second, I think it is important to decide what would constitute the case (i.e., what it is a case of) and where the boundaries of this lie. This often proves more difficult than first appears. And sometimes, partly because of the semifluid nature of the way the case evolves, it is only possible to finally establish what the case is a case of at the end. Nevertheless, it is useful to identify what the case and its boundaries are at the outset to help focus data collection while maintaining an awareness that these may shift. This is emergent design in action.

In deciding the boundary of the case, there are several factors to bear in mind. Is it bounded by an institution or a unit within an institution, by people within an institution, by region, or by project, program or policy,? If we take a school as an example, the case could be comprised of the principal, teachers, and students, or the boundary could be extended to the cleaners, the caretaker, the receptionist, people who often know a great deal about the subnorms and culture of the institution.

If the case is a policy or particular parameter of a policy, the considerations may be slightly different. People will still be paramount—those who generated the policy and those who implemented it—but there is likely also to be a political culture surrounding the policy that had an influence on the way the policy evolved. Would this be part of the case?

Whatever boundary is chosen, this may change in the course of conducting the study when issues arise that can only be understood by going to another level. What transpires in a classroom, for example, if this is the case, is often partly dependent on the support of the school leadership and culture of the institution and this, in turn, to some extent is dependent on what resources are allocated from the local education administration. Much like a series of Russian dolls, one context inside the other.

Unit of analysis

Thinking about what would constitute the unit of analysis— a classroom, an institution, a program, a region—may help in setting the boundaries of the case, and it will certainly help when it comes to analysis. But this is a slightly different issue from deciding what the case is a case of. Taking a health example, the case may be palliative care support, but the unit of analysis the palliative care ward or wards. If you took the palliative care ward as the unit of analysis this would be as much about how palliative care was exercised in this or that ward than issues about palliative care support in general. In other words, you would need to have specific information and context about how this ward was structured and managed to understand how palliative care was conducted in this particular ward. Here, as in the school example above, you would need to consider which of the many people who populate the ward form part of the case—nurses, interns, or doctors only, or does it extend to patients, cleaners, nurse aides, and medical students?

Framing Questions and Issues

The third most important consideration is how to frame the study, and you are likely to do this once you have selected the site or sites for study. There are at least four approaches. You could start with precise questions, foreshadowed issues ( Smith & Pohland, 1974 ), theories, or a program logic. To some extent, your choice will be dictated by the type of case you have chosen, but also by your personal preference for how to conduct it—in either a structured or open way.

Initial questions give structure; foreshadowed issues more freedom to explore. In qualitative case study, foreshadowed issues are more common, allowing scope for issues to change as the study evolves, guided by participants’ perspectives and events in the field. With this perspective, it is more likely that you will generate a theory of the case toward the end, through your interpretation and analysis.

If you are conducting an instrumental case study, staying close to the questions or foreshadowed issues is necessary to be sure you gain data that will illuminate the central focus of the study. This is critical if you are exploring issues across several cases, although it is possible to do a cross-case analysis from cases that have each followed a different route to discovering significant issues.

Opting to start with a theoretical framework provides a basis for formulating questions and issues, but it can also constrain the study to only those questions/issues that fit the framework. The same is true with using program logic to frame the case. This is an approach frequently adopted in evaluation case study where the evaluator, individually or with stakeholders, examines how the aims and objectives of the program relate to the activities designed to promote it and the outcomes and impacts expected. It provides direction, although it can lead to simply confirming what was anticipated, rather than documenting what transpired in the case.

Whichever approach you choose to frame the case, it is useful to think about the rationale or theory for each question and what methods would best enable you to gain an understanding of them. This will not only start a reflexive process of examining your choices—an important aspect of the process of data gathering and interpretation—it will also aid analysis and interpretation further down the track.

Methodology and Methods

Qualitative case study research, as already noted, appeals to subjective ways of knowing and to a primarily qualitative methodology, that captures experiential understanding ( Stake, 2010 , pp. 56–70). It follows that the main methods of data gathering to access this way of knowing will be qualitative. Interviewing, observation, and document analysis are the primary three, often supported by critical incidents, focus groups, cameos, vignettes, diaries/journals, and photographs. Before gathering any primary data, however, it is useful to search relevant existing sources (written or visual) to learn about the antecedents and context of a project, program, or policy as a backdrop to the case. This can sharpen framing questions, avoid unnecessary data gathering, and shorten the time needed in the field.

Given that there are excellent texts on qualitative methods (see, for example, Denzin & Lincoln, 1994 ; Seale, 1999 ; Silverman, 2000 , 2004 ), I will not discuss all potential relevant methods here, but simply focus on the qualities of the primary methods that are particularly appropriate for case study research.

Primary Qualitative Data Gathering Methods

Interviewing.

The most effective style of interviewing in qualitative case study research to gain in-depth data, document multiple perspectives and experiences and explore contested issues is the unstructured interview, active listening and open questioning are paramount, whatever prequestions or foreshadowed issues have been identified. This can include photographs—a useful starting point with certain cultural groups and the less articulate, to encourage them to tell their story through connecting or identifying with something in the image.

The flexibility of unstructured interviewing has three further advantages for understanding participants’ experiences. First, through questioning, probing, listening, and, above all, paying attention to the silences and what they mean, you can get closer to the meaning of participants’ experiences. It is not always what they say.

Second, unstructured interviewing is useful for engaging participants in the process of research. Instead of starting with questions and issues, invite participants to tell their stories or reflect on specific issues, to conduct their own self-evaluative interview, in fact. Not only will they contribute their particular perspective to the case, they will also learn about themselves, thereby making the process of research educative for them as well as for the audiences of the research.

Third, the open-endedness of this style of interviewing has the potential for creating a dialogue between participants and the researcher and between the researcher and the public, if enough of the dialogue is retained in the publication ( Bellah, Madsen, Sullivan, Swidler, & Tipton, 1985 ).

Observations

Observations in case study research are likely to be close-up descriptions of events, activities, and incidents that detail what happens in a particular context. They will record time, place, specific incidents, transactions, and dialogue, and note characteristics of the setting and of people in it without preconceived categories or judgment. No description is devoid of some judgment in selection, of course, but, on the whole, the intent is to describe the scene or event “as it is,” providing a rich, textured description to give readers a sense of what it was like to be there or provide a basis for later interpretation.

Take the following excerpt from a study of the West Bromwich Operatic Society. It is the first night of a new production, The Producers , by this amateur operatic society. This brief excerpt is from a much longer observation of the overture to the first evening’s performance, detailing exactly what the production is, where it is, and why there is such a tremendous sense of atmosphere and expectation surrounding the event. Space prevents including the whole observation, but I hope you can get a glimmer of the passion and excitement that precedes the performance:

Birmingham, late November, 2011, early evening.... Bars and restaurants spruce up for the evening’s trade. There is a chill in the air but the party season is just starting....

A few hundred yards away, past streaming traffic on Suffolk Street, Queensway, an audience is gathering at the New Alexandra Theatre. The foyer windows shine in the orange sodium night. Above each one is the rubric: WORLD CLASS THEATRE.

Inside the preparatory rituals are being observed; sweets chosen, interval drinks ordered and programmes bought. People swap news and titbits about the production.... The bubble of anticipation grows as the 5-minute warning sounds. People make their way to the auditorium. There have been so many nights like this in the past 110 years since a man named William Coutts invested £10,000 to build this palace of dreams.... So many fantasies have been played under this arch: melodramas and pantomimes, musicals and variety.... So many audiences, settling down in their tip-up seats, wanting to be transported away from work, from ordinariness and private troubles.... The dimming lights act like a mother’s hush. You could touch the silence. Boinnng! A spongy thump on a bass drum, and the horns pipe up that catchy, irrepressible, tasteless tune and already you’re singing under your breath, ‘Springtime for Hitler and Germany....’ The orchestra is out of sight in the pit. There’s just the velvet curtain to watch as your fingers tap along. What’s waiting behind? Then it starts it to move. Opening night.... It’s opening night! ( Matarasso, 2012 , pp. 1–2)

For another and different example—a narrative observation of an everyday but unique incident that details date, time, place, and experience—see Simons (2009 , p. 60).

Such naturalistic observations are also useful in contexts where we cannot understand what is going on through interviewing alone—in cultures with which we are less familiar or where key actors may not share our language or have difficulty expressing it. Careful description in these situations can help identify key issues, discover the norms and values that exist in the culture, and, if sufficiently detailed, allow others to cross corroborate what significance we draw from these observations. This last point is very important to avoid the danger in observation of ascribing motivations to people and meanings to transactions.

Finally, naturalistic observations are very important in highly politicized environments, often the case in commissioned evaluation case study, where individuals in interview may try to elude the “truth” or press on you that their view is the “right” view of the situation. In these contexts, naturalistic observations not only enable you to document interactions as you perceive them, but they also provide a cross-check on the veracity of information obtained in interviews.

Document analysis

Analysis of documents, as already intimated, is useful for establishing what historical antecedents might exist to provide a springboard for contemporaneous data gathering. In most cases, existing documents are also extremely pertinent for understanding the policy context.

In a national policy case study I conducted on a major curriculum change, the importance of preexisting documentation was brought home to me sharply when certain documentation initially proved elusive to obtain. It was difficult to believe that it did not exist, as the evolution of the innovation involved several parties who had not worked together before. There was bound, I thought, to be minuted meetings sharing progress and documentation of the “new” curriculum. In the absence of some crucial documents, I began to piece together the story through interviewing. Only there were gaps, and certain issues did not make sense.

It was only when I presented two versions of what I discerned had transpired in the development of this initiative in an interim report eighteen months into the study that things started to change. Subsequent to the meeting at which the report was presented, the “missing” documents started to appear. Suddenly found. What lay behind the “missing documents,” something I suspected from what certain individuals did and did not say in interview, was a major difference of view about how the innovation evolved, who was key in the process, and whose voice was more important in the context. Political differences, in other words, that some stakeholders were trying to keep from me. The emergence of the documents enabled me to finally produce an accurate and fair account.

This is an example of the importance of having access to all relevant documents relating to a program or policy in order to study it fairly. The other major way in which document analysis is useful in case study is for understanding the values, explicit and hidden, in policy and program documents and in the organization where the program or policy is implemented. Not to be ignored as documents are photographs, and these, too, can form the basis of a cultural and value analysis of an organization ( Prosser, 2000 ).

Creative artistic approaches

Increasingly, some case study researchers are employing creative approaches associated with the arts as a means of data gathering and analysis. Artistic approaches have often been used in representing findings, but less frequently in data gathering and interpretation ( Simons & McCormack, 2007 ). A major exception is the work of Richardson (1994) , who sees the very process of writing as an interpretative act, and of Cancienne and Snowber (2003) , who argue for movement as method.

The most familiar of these creative and artistic forms are written—narratives and short stories ( Clandinin & Connelly, 2000 ; Richardson, 1994 ; Sparkes, 2002 ), poems or poetic form ( Butler-Kisber, 2010 ; Duke, 2007 ; Richardson, 1997 ; Sparkes & Douglas, 2007 ), cameos of people, or vignettes of situations. These can be written by participants or by the researcher or developed in partnership. They can also be shared with participants to further interpret the data. But photographs also have a long history in qualitative research for presenting and constructing understanding ( Butler-Kisber, 2010 ; Collier, 1967 ; Prosser, 2000 ; Rugang, 2006 ; Walker, 1993 ).

Less common are other visual forms of gathering data, such as “draw and write” ( Sewell, 2011 ), artefacts, drawings, sketches, paintings, and collages, although all forms are now on the increase. For examples of the use of collage in data gathering, see Duke (2007) and Butler-Kisber (2010) , and for charcoal drawing, Elliott (2008) .

In qualitative inquiry broadly, these creative approaches are now quite common. And in the context of arts and health in particular (see, for example, Frank, 1997 ; Liamputtong & Rumbold, 2008 ; Spouse, 2000 ), we can see how artistic approaches illuminate in-depth understanding. However, in case study research to date, I think narrative forms have tended to be most prominent.

Finally, for capturing the quality and essence of peoples’ experience, nothing could be more revealing than a recording of their voices. Video diaries—self-evaluative portrayals by individuals of their perspectives, feelings, or experience of an event or situation—are a most potent way both of gaining understanding and communicating that to others. It is rather more difficult to gain access for observational videos, but they are useful for documentation and have the potential to engage participants and stakeholders in the interpretation.

Getting It All Together

Case study is so often associated with story or with a report of some event or program that it is easy to forget that much analysis and interpretation has gone on before we reach this point. In many case study reports, this process is hidden, leaving the reader with little evidence on which to assess the validity of the findings and having to trust the one who wrote the tale.

This section briefly outlines possibilities, first, for analyzing and interpreting data, and second, for how to communicate the findings to others. However it is useful to think of these together and indeed, at the start, because decisions about how you report may influence how you choose to make sense of the data. Your choice may also vary according to the context of the study—what is expected or acceptable—and your personal predilections, whether you prefer a more rational than intuitive mode of analysis, for example, or a formal or informal style of writing up that includes images, metaphor, narratives, or poetic forms.

Analyzing and Interpreting Data

When it comes to making sense of data, I make a distinction between analysis—a formal inductive process that seeks to explain—and interpretation, a more intuitive process that gains understanding and insight from a holistic grasp of data, although these may interact and overlap at different stages.

The process, whichever emphasis you choose, is one of reducing or transforming a large amount of data to themes that can encapsulate the overarching meaning in the data. This involves sorting, refining, and refocusing data until they make sense. It starts at the beginning with preliminary hunches, sometimes called “interpretative asides” or “working hypotheses,” later moving to themes, analytic propositions, or a theory of the case.

There are many ways to conduct this process. Two strategies often employed are concept mapping —a means of representing data visually to explore links between related concepts—and progressive focusing ( Parlett & Hamilton, 1976 ), the gradual reframing of initially identified issues into themes that are then further interpreted to generate findings. Each of these strategies tends to have three stages: initial sense making, identification of themes, and examination of patterns and relationships between them.

If taking a formal analytic approach to the task, the data would likely be broken down into segments or datasets (coded and categorized) and then reordered and explored for themes, patterns, and possible propositions. If adopting a more intuitive process, you might focus on identifying insights through metaphors and images, lateral thinking, or puzzling over paradoxes and ambiguities in the data, after first immersing yourself in the total dataset, reading and re-reading interview scripts, observations and field notes to get a sense of the whole. Trying out different forms of making sense through poetry, vignettes, cameos, narratives, collages, and drawing are further creative ways to interpret data, as are photographs taken in the case arranged to explain or tell the story of the case.

Reporting Case Study Research

Narrative structure and story.

As indicated in the introduction, telling a story is often associated with case study and some think this is what a case study is. In one sense, it is and, given that story is the natural way in which we learn ( Okri, 1997 ), it is a useful framework both for gathering data and for communicating case study findings. Not any story will do however. To count as research, it must be authentic, grounded in data, interpreted and analyzed to convey the meaning of the case.

There are several senses in which story is appropriate in qualitative case study: in capturing stories participants tell, in generating a narrative structure that makes sense of the case (i.e., the story you will tell), and in deciding how you communicate this narrative (i.e., in story form). If you choose a written story form (and advice here can be sought from Harrington (2003) and Caulley (2008) ), it needs to be clearly structured, well written, and contain only the detail that is necessary to give readers the vicarious experience of what it was like in the case. If the story is to be communicated in other ways, through, for example, audio or videotape, or computer or personal interaction, the same applies, substituting visual and interpersonal skill for written.

Matching forms of reporting to audience

The art of reporting is strongly connected to usability, so forms of reporting need to connect to the audiences we hope to inform: how they learn, what kind of evidence they value, and what kind of reporting maximizes the chances they will use the findings to promote policies and programs in the interests of beneficiaries. As Okri (1997) further reminds us, the writer only does half the work; the reader does the other (p. 41).

There may be other considerations as well: how open are commissioners to receiving stories of difficulties, as well as success stories? What might they need to hear beyond what is sought in the technical brief? And through what style of reporting would you try and persuade them? If conducting noncommissioned case study research, the scope for different forms of reporting is wider. In academia, for instance, many institutions these days accept creative and artistic forms of reporting when supported by supervisors and appreciated by examiners.

Styles of Reporting

The most obvious form of reporting is linear, often starting with a short executive summary and a brief description of focus and context, followed by methodology, the case study or thematic analysis, findings, and conclusions or implications. Conclusion-led reporting is similar in terms of its formality, but simply starts the other way around. From the conclusions drawn from the analyzed data, it works backward to tell the story through narrative, verbatim, and observational data of how these conclusions were reached. Both have a strong story line. The intent is analytic and explanatory.

Quite a different approach is to engage the reader in the experience and veracity of the case. Rather like constructing a portrait or editing a documentary film, this involves the sifting, constructing, re-ordering of frames, events and episodes to tell a coherent story primarily through interview excerpts, observations, vignettes, and critical incidents that depict what transpired in the case. Interpretation is indirect through the weaving of the data. The story can start at any point provided the underlying narrative structure is maintained to establish coherence ( House, 1980 , p. 116).

Different again, and from the other end of a continuum, is a highly interpretative account that may use similar ways of presenting data but weaves a story from the outset that is highly interpretative. Engaging metaphor, images, short stories, contradictions, paradoxes, and puzzles, it is invariably interesting to read and can be most persuasive. However, the evidence is less visible and therefore less open to alternative interpretations.

Even more persuasive is a case study that uses artistic forms to communicate the story of the case. Paintings, poetic form, drawings, photography, collage, and movement can all be adopted to report findings, whether the data was acquired using these forms or by other means. The arts-based inquiry movement ( Mullen & Finley, 2003 ) has contributed hugely to the validation and legitimation of artistic and creative ways of representing qualitative research findings. The journal Qualitative Inquiry contains many good examples, but see also Liamputtong & Rumbold (2008) . Such artistic forms of representation may not be for everyone or appropriate in some contexts, but they do have the power to engage an audience and the potential to facilitate use.

Generalization in Case Study Research

One of the potential limitations of case study often proposed is that it is impossible to generalize. This is not so. However, the way in which one generalizes from a case is different from that adopted in traditional forms of social science research that utilize large samples (randomly selected) and statistical procedures and which assume regularities in the social world that allow cause and effect to be determined. In this form of research inferences from data are stated as formal propositions that apply to all in the target population. See Donmoyer (1990) for an argument on the restricted nature of this form of generalization when considering single-case studies.

Making inferences from cases with a qualitative data set arises more from a process of interpretation in context, appealing to tacit and situated understanding for acceptance of their validity. Such inferences are possible where the context and experience of the case is richly described so the reader can recognize and connect with the events and experiences portrayed. There are two ways to examine how to reach these generalized understandings. One is to generalize from the case to other cases of a similar or dissimilar nature. The other is to see what we learn in-depth from the uniqueness of the single case itself.

Generalizing from the Single Case

A common approach to generalization and one most akin to a propositional form is cross-case generalization. In a collective or multi-site case study, each case is explored to see if issues that arise in one case also exist in other cases and what interconnecting themes there are between them. This kind of generalization has a degree of abstraction and potential for theorizing and is often welcomed by commissioners of research concerned that findings from the single case do not provide an adequate or “safe” basis for policy determination.

However, there are four additional ways to generalize from the single case, all of which draw more on tacit knowledge and recognition of context, although in different ways. In naturalistic generalization , first proposed by Stake (1978) , generalization is reached on the basis of recognition of similarities and differences to cases with which we are familiar. To enable such recognition, the case needs to feature rich description; people’s voices; and enough detail of time, place, and context to provide a vicarious experience to help readers discern what is similar and dissimilar to their own context ( Stake, 1978 ).

Situated generalization ( Simons, Kushner, Jones, & James, 2003 ) is close to the concept of naturalistic generalization in relying for its generality on retaining a connectedness with the context in which it first evolved. However, it has an extra dimension in a practice context. This notion of generalization was identified in an evaluation of a research project that engaged teachers in and with research. Here, in addition to the usual validity criteria to establish the warrant for the findings, the generalization was seen as dependable if trust existed between those who conducted the research (teachers, in this example) and those thinking about using it (other teachers). In other words, beyond the technical validity of the research, teachers considered using the findings in their own practice because they had confidence in those who generated them. This is a useful way to think about generalization if we wish research findings to improve professional practice.

The next two concepts of generalization— concept and process generalization —relate more to what you discover in making sense of the case. As you interpret and analyze, you begin to generate a theory of the case that makes sense of the whole. Concepts may be identified that make sense in the one case but have equal significance in other cases of a similar kind, even if the contexts are different.

It is the concept that generalizes, not the specific content or context. This may be similar to the process Donmoyer (2008) identifies of “intellectual generalization” (quoted by Butler-Kisber, 2010 , p. 15) to indicate the cognitive understanding one can gain from qualitative accounts even if settings are quite different.

The same is true for generalization of a process. It is possible to identify a significant process in one case (or several cases) that is transferable to other contexts, irrespective of the precise content and contexts of those other cases. An example here is the collaborative model for sustainable school self-evaluation I identified in researching school self-evaluation in a number of schools and countries ( Simons, 2002 ). Schools that successfully sustained school self-evaluation had an infrastructure that was collaborative at all stages of the evaluation process from design to conduct of the study, to analyzing the results and to reporting the findings. This ensured that the whole school was involved and that results were discussed and built into the ongoing development of school policies and practice. In other cases, different processes may be discovered that have applicability in a range of contexts. As with concept generalization, it is the process that generalizes not the substantive content or specific context.

Particularization

The forms of generalization discussed above are useful when we have to justify case study in a research or policy context. But the overarching justification for how we learn from case study is particularization —a rich portrayal of insights and understandings interpreted in the particular context. Several authors have made this point ( Stake, 1995 ; Flyvberg, 2006 ; Simons 2009 ). Stake puts it most sharply when he observes that “The real business of case study is particularization, not generalization” (p. 8), referring here to the main reason for studying the singular, which is to understand the uniqueness of the case itself.

My perspective (explored further in Simons, 1996 ; Simons, 2009 , p. 239; Simons & McCormack, 2007 ) is similar in that I believe the “real” strength of case study lies in the insights we gain from in-depth study of the particular. But I also argue for the universality of such insights—if we get it “right.” By which I mean that if we are able to capture and report the uniqueness, the essence, of the case in all its particularity and present this in a way we can all recognize, we will discover something of universal significance. This is something of a paradox. The more you learn in depth about the particularity of one person, situation, or context, the more likely you are to discover something universal. This process of reaching understanding has support both from the way in which many discoveries are made in science and in how we learn from artists, poets, and novelists, who reach us by communicating a recognizable truth about individuals, human relationships, and/or social contexts.

This concept of particularization is far from new, as the quotation from a preface to a book written in 1908 attests. Stephen Reynolds, the author of A Poor Man’s House , notes that the substance of the book was first recorded in a journal, kept for purposes of fiction, and in letters to one of his friends, but fiction proved an inappropriate medium. He felt that the life and the people were so much better than anything he could invent. The book therefore consists of the journal and letters drawn together to present a picture of a typical poor man’s house and life, much as we might draw together a range of data to present a case study. It is not the substance of the book that concerns us here but the methodological relevance to case study research. Reynolds notes that the conclusions expressed are tentative and possibly go beyond this man’s life, so he thought some explanation of the way he arrived at them was needed:

Educated people usually deal with the poor man’s life deductively; they reason from the general to the particular; and, starting with a theory, religious, philanthropic, political, or what not, they seek, and too easily find, among the millions of poor, specimens—very frequently abnormal—to illustrate their theories. With anything but human beings, that is an excellent method. Human beings, unfortunately, have individualities. They do what, theoretically, they ought not to do, and leave undone those things they ought to do. They are even said to possess souls—untrustworthy things beyond the reach of sociologists. The inductive method—reasoning from the particular to the general... should at least help to counterbalance the psychological superficiality of the deductive method. ( Reynolds, 1908 : preface) 1

Slightly overstated perhaps, but the point is well made. In our search for general laws, we not only lose sight of the uniqueness and humanity of individuals, but reduce them in the process, failing to present their experience in any “real” sense. What is astonishing about the quotation is that it was written over a century ago and yet many still argue today that you cannot generalize from the particular.

Going even further back, in 1798, Blake proclaimed that “To Generalize is to be an Idiot. To Particularize is the Alone Distinction of Merit.” In research, we may not wish to make such a strong distinction: these processes both have their uses in different kinds of research. But there is a major point here for the study of the particular that Wilson (2008) notes in commenting on Blake’s perception when he says: “Favouring the abstract over the concrete, one ‘sees all things only thro’ the narrow chinks of his cavern”’ (referring here to Blake’s The Marriage of Heaven and Hell [1793]; in Wilson, 2008 , p. 62). The danger Wilson is pointing to here is that abstraction relies heavily on what we know from our past understanding of things, and this may prevent us experiencing a concrete event directly or “apprehend[ing] a particular moment” ( Wilson, 2008 , p. 63).

Blake had a different mission, of course, than case researchers, and he was not himself free from abstractions, as Wilson points out, although he fought hard “to break through mental barriers to something unique and living” ( Wilson, 2008 , p. 65). It is this search for the “unique and living” and experiencing the “isness” of the particular that we should take from the Blake example to remind ourselves of the possibility of discovering something “new,” beyond our current understanding of the way things are.

Focusing on particularization does not diminish the usefulness of case study research for policy makers or practitioners. Grounded in recognizable experience, the potential is there to reach a range of audiences and to facilitate use of the findings. It may be more difficult for those who seek formal generalizations that seem to offer a safe basis for policy making to accept case study reports. However, particular stories often hold the key to why policies have or have not worked well in the past. It is not necessary to present long cases—a criticism frequently levelled—to demonstrate the story of the case. Such case stories can be most insightful for policy makers who, like many of us in everyday life, often draw inferences from a single instance or case, whatever the formal evidence presented. “I am reminded of the story of....”

The case for studying the particular to inform practice in professional contexts needs less persuasion because practitioners can recognize the content and context quite readily and make the inference to their own particular context ( Simons et al., 2003 ). In both sets of circumstances—policy and practice—it is more a question of whether the readers of our case research accept the validity of findings determined in this way, how they choose to learn, and our skill in telling the case study story.

Conclusion and Future Directions

In this chapter, I have presented an argument for case study research, making the case, in particular, for using qualitative methods to highlight what it is that qualitative case study research can bring to the study of social and educational programs. I outlined the various ways in which case study is commonly used before focusing directly on case study as a major mode of research inquiry, noting characteristics it shares with other qualitative methodologies, as well as itsdifference and the difficulties it is sometimes perceived to have. The chapter emphasizes the importance of thinking through what the case is, to be sure that the issues explored and the data generated do illuminate this case and not any other.

But there is still more to be done. In particular, I think we need to be more adventurous in how we craft and report the case. I suspect we may have been too cautious in the past in how we justified case study research, borrowing concepts from other disciplines and forms of educational research. More than 40 years on, it is time to take a greater risk—in demonstrating the intrinsic nature of case study and what it can offer to our understanding of human and social situations.

I have already drawn attention to the need to design the case, although this could be developed further to accentuate the uniqueness of the particular case. One way to do this is to feature individuals more in the design itself, not only to explore programs and policies through perspectives of key actors or groups and transactions between them, which to some extent happens already, but also to get them to characterize what makes the context unique. This is the reversal of many a design framework that starts with the logic of a program and takes forward the argument for personal evaluation ( Kushner, 2000 ), noted in the interlude on evaluation. Apart from this attention to design, there are three other issues I think we need to explore further: the warrant for creative methods in case study, more imaginative reporting; and how we learn from a study of the singular.

Warrant for More Creative Methods in Case Study Research

The promise that creative methods have for eliciting in-depth understanding and capturing the unusual, the idiosyncratic, the uniqueness of the case, was mentioned in the methods section. Yet, in case study research, particularly in program and policy contexts, we have few good examples of the use of artistic approaches for eliciting and interpreting data, although more, as acknowledged later, for presenting it. This may be because case study research is often conducted in academic or policy environments, where propositional ways of knowing are more valued.

Using creative and artistic forms in generating and interpreting case study data offers a form of evidence that acknowledges experiential understanding in illuminating the uniqueness of the case. The question is how to establish the warrant for this way of knowing and persuade others of its virtue. The answer is simple. By demonstrating the use of these methods in action, by arguing for a different form of validity that matches the intrinsic nature of the method, and, above all, by good examples.

Representing Findings to Engage Audiences in Learning

In evaluative and research policy contexts, where case study is often the main mode of inquiry or part of a broader study, case study reports often take a formal structure or sometimes, where the context is receptive, a portrayal or interpretative form. But, too often, the qualitative is an add-on to a story told by other means or reduced to issues in which the people who gave rise to the data are no longer seen. However, there are many ways to put them center stage.

Tell good stories and tell them well. Or, let key actors tell their own stories. Explore the different ways technology can help. Make video clips that demonstrate events in context, illustrate interactions between people, give voice to participants—show the reality of the program, in other words. Use graphics to summarize key issues and interactive, cartoon technology, as seen on some TED presentations, to summarize and visually show the complexity of the case. Video diaries were mentioned in the methods section: seeing individuals tell their tales directly is a powerful way of communicating, unhindered by “our” sense making. Tell photo stories. Let the photos convey the narrative, but make sure the structure of the narrative is evident to ensure coherence. These are just the beginnings. Those skilled in information technology could no doubt stretch our imagination further.

One problem and a further question concerns our audiences. Will they accept these modes of communication? Maybe not, in some contexts. However, there are three points I wish to leave you with. First, do not presume that they won’t. If people are fully present in the story and the complexity is not diminished, those reading, watching, or hearing about the case will get the message. If you are worried about how commissioners might respond, remember that they are no different from any other stakeholder or participant when it comes to how they learn from human experience. Witness the reference to Okri (1997) earlier about how we learn.

Second, when you detect that the context requires a more formal presentation of findings, respond according to expectation but also include elements of other forms of presentation. Nudge a little in the direction of creativity. Third, simply take a chance, that risk I spoke about earlier. Challenge the status quo. Find situations and contexts where you can fully represent the qualitative nature of the experience in the cases you study with creative forms of interpretation and representation. And let the audience decide.

Learning from a Study of the Singular

Finally, to return to the issue of “generalization” in case study that worries some audiences. I pointed out in the generalization section several ways in which it is possible to generalize from case study research, not in a formal propositional sense or from a case to a population, but by retaining a connection with the context in which the generalization first arose—that is, to realize in-depth understanding in context in different circumstances and situations. However, I also emphasized that, in many instances, it is particularization from which we learn. That is the point of the singular case study, and it is an art to perceive and craft the case in ways that we can.

Acknowledgments

Parts of this chapter build on ideas first explored in Simons, 2009 .

I am grateful to Bob Williams for pointing out the relevance of this quotation from Reynolds to remind us that “there is nothing new under the sun” and that we sometimes continue to engage endlessly in debates that have been well rehearsed before.

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The Case Study as Research Method: A Practical Handbook

Qualitative Research in Accounting & Management

ISSN : 1176-6093

Article publication date: 21 June 2011

Scapens, R.W. (2011), "The Case Study as Research Method: A Practical Handbook", Qualitative Research in Accounting & Management , Vol. 8 No. 2, pp. 201-204. https://doi.org/10.1108/11766091111137582

Emerald Group Publishing Limited

Copyright © 2011, Emerald Group Publishing Limited

This book aims to provide case‐study researchers with a step‐by‐step practical guide to “help them conduct the study with the required degree of rigour” (p. xi).

It seeks to “demonstrate that the case study is indeed a scientific method” (p. 104) and to show “the usefulness of the case method as one tool in the researcher's methodological arsenal” (p. 105). The individual chapters cover the various stages in conducting case‐study research, and each chapter sets out a number of practical steps which have to be taken by the researcher. The following are the eight stages/chapters and, in brackets, the number of steps in each stages:

Assessing appropriateness and usefulness (4).

Ensuring accuracy of results (21).

Preparation (6).

Selecting cases (4).

Collecting data (7).

Analyzing data (4).

Interpreting data (3).

Reporting results (4).

It is particularly noticeable that ensuring accuracy of results has by far the largest number of number of steps – 21 steps compared to seven or fewer steps in the other stages. This reflects Gagnon's concern to demonstrate the scientific rigour of case‐study research. In the forward, he explains that the book draws on his experience in conducting his own PhD research, which was closely supervised by three professors, one of whom was inclined towards quantitative research. Consequently, his research was underpinned by the principles and philosophy of quantitative research. This is clearly reflected in the approach taken in this book, which seeks to show that case‐study research is just as rigorous and scientific as quantitative research, and it can produce an objective and accurate representation of the observed reality.

There is no discussion of the methodological issues relating to the use of case‐study research methods. This is acknowledged in the forward, although Gagnon refers to them as philosophical or epistemological issues (p. xii), as he tends to use the terms methodology and method interchangeably – as is common in quantitative research. Although he starts (step 1.1) by trying to distance case and other qualitative research from the work of positivists, arguing that society is socially constructed, he nevertheless sees social reality as objective and independent of the researcher. So for Gagnon, the aim of case research is to accurately reflect that reality. At various points in the book the notion of interpretation is used – evidence is interpreted and the (objective) case findings have to be interpreted.

So although there is a distancing from positivist research (p. 1), the approach taken in this book retains an objective view of the social reality which is being researched; a view which is rather different to the subjective view of reality taken by many interpretive case researchers. This distinction between an objective and a subjective view of the social reality being researched – and especially its use in contrasting positivist and interpretive research – has its origins the taxonomy of Burrell and Morgan (1979) . Although there have been various developments in the so‐called “objective‐subjective debate”, and recently some discussion in relation to management accounting research ( Kakkuri‐Knuuttila et al. , 2008 ; Ahrens, 2008 ), this debate is not mentioned in the book. Nevertheless, it is clear that Gagnon is firmly in the objective camp. In a recent paper, Johnson et al. (2006, p. 138) provide a more contemporary classification of the different types of qualitative research. In their terms, the approach taken in this book could be described as neo‐empiricist – an approach which they characterise as “qualitative positivists”.

The approach taken in this handbook leaves case studies open to the criticisms that they are a small sample, and consequently difficult to generalise, and to arguments that case studies are most appropriate for exploratory research which can subsequently be generalised though quantitative research. Gagnon explains that this was the approach he used after completing his thesis (p. xi). The handbook only seems to recognise two types of case studies, namely exploratory and raw empirical case studies – the latter being used where “the researcher is interested in a subject without having formed any preconceived ideas about it” (p. 15) – which has echoes of Glaser and Strauss (1967) . However, limiting case studies to these two types ignores other potential types; in particular, explanatory case studies which are where interpretive case‐study research can make important contributions ( Ryan et al. , 2002 ).

This limited approach to case studies comes through in the practical steps which are recommended in the handbook, and especially in the discussion of reliability and validity. The suggested steps seem to be designed to keep very close to the notions of reliability and validity used in quantitative research. There is no mention of the recent discussion of “validity” in interpretive accounting research, which emphasises the importance of authenticity and credibility and their implications for writing up qualitative and case‐study research ( Lukka and Modell, 2010 ). Although the final stage of Gagnon's handbook makes some very general comments about reporting the results, it does not mention, for example, Baxter and Chua's (2008) paper in QRAM which discusses the importance of demonstrating authenticity, credibility and transferability in writing qualitative research.

Despite Gagnon's emphasis on traditional notions of reliability and validity the handbook provides some useful practical advice for all case‐study researchers. For example, case‐study research needs a very good research design; case‐study researchers must work hard to gain access to and acceptance in the research settings; a clear strategy is needed for data collection; the case researcher should create field notes (in a field notebook, or otherwise) to record all the thoughts, ideas, observations, etc. that would not otherwise be collected; and the vast amount of data that case‐study research can generate needs to be carefully managed. Furthermore, because of what Gagnon calls the “risk of mortality” (p. 54) (i.e. the risk that access to a research site may be lost – for instance, if the organisation goes bankrupt) it is crucial for some additional site(s) to be selected at the outset to ensure that the planned research can be completed. This is what I call “insurance cases” when talking to my own PhD students. Interestingly, Gagnon recognises the ethical issues involved in doing case studies – something which is not always mentioned by the more objectivist type of case‐study researchers. He emphasises that it is crucial to honour confidentiality agreements, to ensure data are stored securely and that commitments are met and promises kept.

There is an interesting discussion of the advantages and disadvantages of using computer methods in analysing data (in stage 6). However, the discussion of coding appears to be heavily influenced by grounded theory, and is clearly concerned with producing an accurate reflection of an objective reality. In addition, Gagnon's depiction of case analysis is overly focussed on content analysis – possibly because it is a quantitative type of technique. There is no reference to the other approaches available to qualitative researchers. For example, there is no mention of the various visualisation techniques set out in Miles and Huberman (1994) .

To summarise, Gagnon's book is particularly useful for case‐study researchers who see the reality they are researching as objective and researcher independent. However, this is a sub‐set of case‐study researchers. Although some of the practical guidance offered is relevant for other types of case‐study researchers, those who see multiple realities in the social actors and/or recognise the subjectivity of the research process might have difficulty with some of the steps in this handbook. Gagnon's aim to show that the case study is a scientific method, gives the handbook a focus on traditional (quantitatively inspired) notions rigour and validity, and a tendency to ignore (or at least marginalise) other types of case study research. For example, the focus on exploratory cases, which need to be supplemented by broad based quantitative research, overlooks the real potential of case study research which lies in explanatory cases. Furthermore, Gagnon is rather worried about participant research, as the researcher may play a role which is “not consistent with scientific method” (p. 42), and which may introduce researcher bias and thereby damage “the impartiality of the study” (p. 53). Leaving aside the philosophical question about whether any social science research, including quantitative research, can be impartial, this stance could severely limit the potential of case‐study research and it would rule out both the early work on the sociology of mass production and the recent calls for interventionist research. Clearly, there could be a problem where a researcher is trying to sell consulting services, but there is a long tradition of social researchers working within organisations that they are studying. Furthermore, if interpretive research is to be relevant for practice, researchers may have to work with organisations to introduce new ideas and new ways of analysing problems. Gagnon would seem to want to avoid all such research – as it would not be “impartial”.

Consequently, although there is some good practical advice for case study researchers in this handbook, some of the recommendations have to be treated cautiously, as it is a book which sees case‐study research in a very specific way. As mentioned earlier, in the Forward Gagnon explicitly recognises that the book does not take a position on the methodological debates surrounding the use of case studies as a research method, and he says that “The reader should therefore use and judge this handbook with these considerations in mind” (p. xii). This is very good advice – caveat emptor .

Ahrens , T. ( 2008 ), “ A comment on Marja‐Liisa Kakkuri‐Knuuttila ”, Accounting, Organizations and Society , Vol. 33 Nos 2/3 , pp. 291 ‐ 7 , Kari Lukka and Jaakko Kuorikoski.

Baxter , J. and Chua , W.F. ( 2008 ), “ The field researcher as author‐writer ”, Qualitative Research in Accounting & Management , Vol. 5 No. 2 , pp. 101 ‐ 21 .

Burrell , G. and Morgan , G. ( 1979 ), Sociological Paradigms and Organizational Analysis , Heinneman , London .

Glaser , B.G. and Strauss , A.L. ( 1967 ), The Discovery of Grounded Theory: Strategies for Qualitative Research , Aldine , New York, NY .

Johnson , P. , Buehring , A. , Cassell , C. and Symon , G. ( 2006 ), “ Evaluating qualitative management research: towards a contingent critieriology ”, International Journal of Management Reviews , Vol. 8 No. 3 , pp. 131 ‐ 56 .

Kakkuri‐Knuuttila , M.‐L. , Lukka , K. and Kuorikoski , J. ( 2008 ), “ Straddling between paradigms: a naturalistic philosophical case study on interpretive research in management accounting ”, Accounting, Organizations and Society , Vol. 33 Nos 2/3 , pp. 267 ‐ 91 .

Lukka , K. and Modell , S. ( 2010 ), “ Validation in interpretive management accounting research ”, Accounting, Organizations and Society , Vol. 35 , pp. 462 ‐ 77 .

Miles , M.B. and Huberman , A.M. ( 1994 ), Qualitative Data Analysis: A Source Book of New Methods , 2nd ed. , Sage , London .

Ryan , R.J. , Scapens , R.W. and Theobald , M. ( 2002 ), Research Methods and Methodology in Finance and Accounting , 2nd ed. , Thomson Learning , London .

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• Case Study | Definition, Examples & Methods

Case Study | Definition, Examples & Methods

Published on 5 May 2022 by Shona McCombes . Revised on 30 January 2023.

A case study is a detailed study of a specific subject, such as a person, group, place, event, organisation, or phenomenon. Case studies are commonly used in social, educational, clinical, and business research.

A case study research design usually involves qualitative methods , but quantitative methods are sometimes also used. Case studies are good for describing , comparing, evaluating, and understanding different aspects of a research problem .

Table of contents

When to do a case study, step 1: select a case, step 2: build a theoretical framework, step 3: collect your data, step 4: describe and analyse the case.

A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject. It allows you to explore the key characteristics, meanings, and implications of the case.

Case studies are often a good choice in a thesis or dissertation . They keep your project focused and manageable when you don’t have the time or resources to do large-scale research.

You might use just one complex case study where you explore a single subject in depth, or conduct multiple case studies to compare and illuminate different aspects of your research problem.

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Once you have developed your problem statement and research questions , you should be ready to choose the specific case that you want to focus on. A good case study should have the potential to:

• Provide new or unexpected insights into the subject
• Challenge or complicate existing assumptions and theories
• Propose practical courses of action to resolve a problem
• Open up new directions for future research

Unlike quantitative or experimental research, a strong case study does not require a random or representative sample. In fact, case studies often deliberately focus on unusual, neglected, or outlying cases which may shed new light on the research problem.

If you find yourself aiming to simultaneously investigate and solve an issue, consider conducting action research . As its name suggests, action research conducts research and takes action at the same time, and is highly iterative and flexible. 

However, you can also choose a more common or representative case to exemplify a particular category, experience, or phenomenon.

While case studies focus more on concrete details than general theories, they should usually have some connection with theory in the field. This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to:

• Exemplify a theory by showing how it explains the case under investigation
• Expand on a theory by uncovering new concepts and ideas that need to be incorporated
• Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions

To ensure that your analysis of the case has a solid academic grounding, you should conduct a literature review of sources related to the topic and develop a theoretical framework . This means identifying key concepts and theories to guide your analysis and interpretation.

There are many different research methods you can use to collect data on your subject. Case studies tend to focus on qualitative data using methods such as interviews, observations, and analysis of primary and secondary sources (e.g., newspaper articles, photographs, official records). Sometimes a case study will also collect quantitative data .

The aim is to gain as thorough an understanding as possible of the case and its context.

In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject.

How you report your findings depends on the type of research you are doing. Some case studies are structured like a standard scientific paper or thesis, with separate sections or chapters for the methods , results , and discussion .

Others are written in a more narrative style, aiming to explore the case from various angles and analyse its meanings and implications (for example, by using textual analysis or discourse analysis ).

In all cases, though, make sure to give contextual details about the case, connect it back to the literature and theory, and discuss how it fits into wider patterns or debates.

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Formulating Research Aims and Objectives

Formulating research aim and objectives in an appropriate manner is one of the most important aspects of your thesis. This is because research aim and objectives determine the scope, depth and the overall direction of the research. Research question is the central question of the study that has to be answered on the basis of research findings.

Research aim emphasizes what needs to be achieved within the scope of the research, by the end of the research process. Achievement of research aim provides answer to the research question.

Research objectives divide research aim into several parts and address each part separately. Research aim specifies WHAT needs to be studied and research objectives comprise a number of steps that address HOW research aim will be achieved.

As a rule of dumb, there would be one research aim and several research objectives. Achievement of each research objective will lead to the achievement of the research aim.

Consider the following as an example:

Research title: Effects of organizational culture on business profitability: a case study of Virgin Atlantic

Research aim: To assess the effects of Virgin Atlantic organizational culture on business profitability

Following research objectives would facilitate the achievement of this aim:

• Analyzing the nature of organizational culture at Virgin Atlantic by September 1, 2022
• Identifying factors impacting Virgin Atlantic organizational culture by September 16, 2022
• Analyzing impacts of Virgin Atlantic organizational culture on employee performances by September 30, 2022
• Providing recommendations to Virgin Atlantic strategic level management in terms of increasing the level of effectiveness of organizational culture by October 5, 2022

Figure below illustrates additional examples in formulating research aims and objectives:

Formulation of research question, aim and objectives

Common mistakes in the formulation of research aim relate to the following:

1. Choosing the topic too broadly . This is the most common mistake. For example, a research title of “an analysis of leadership practices” can be classified as too broad because the title fails to answer the following questions:

a) Which aspects of leadership practices? Leadership has many aspects such as employee motivation, ethical behaviour, strategic planning, change management etc. An attempt to cover all of these aspects of organizational leadership within a single research will result in an unfocused and poor work.

b) An analysis of leadership practices in which country? Leadership practices tend to be different in various countries due to cross-cultural differences, legislations and a range of other region-specific factors. Therefore, a study of leadership practices needs to be country-specific.

c) Analysis of leadership practices in which company or industry? Similar to the point above, analysis of leadership practices needs to take into account industry-specific and/or company-specific differences, and there is no way to conduct a leadership research that relates to all industries and organizations in an equal manner.

Accordingly, as an example “a study into the impacts of ethical behaviour of a leader on the level of employee motivation in US healthcare sector” would be a more appropriate title than simply “An analysis of leadership practices”.

2. Setting an unrealistic aim . Formulation of a research aim that involves in-depth interviews with Apple strategic level management by an undergraduate level student can be specified as a bit over-ambitious. This is because securing an interview with Apple CEO Tim Cook or members of Apple Board of Directors might not be easy. This is an extreme example of course, but you got the idea. Instead, you may aim to interview the manager of your local Apple store and adopt a more feasible strategy to get your dissertation completed.

3. Choosing research methods incompatible with the timeframe available . Conducting interviews with 20 sample group members and collecting primary data through 2 focus groups when only three months left until submission of your dissertation can be very difficult, if not impossible. Accordingly, timeframe available need to be taken into account when formulating research aims and objectives and selecting research methods.

Moreover, research objectives need to be formulated according to SMART principle,

 where the abbreviation stands for specific, measurable, achievable, realistic, and time-bound.

Examples of SMART research objectives

At the conclusion part of your research project you will need to reflect on the level of achievement of research aims and objectives. In case your research aims and objectives are not fully achieved by the end of the study, you will need to discuss the reasons. These may include initial inappropriate formulation of research aims and objectives, effects of other variables that were not considered at the beginning of the research or changes in some circumstances during the research process.

John Dudovskiy

• Open access
• Published: 27 June 2011

The case study approach

• Sarah Crowe 1 ,
• Kathrin Cresswell 2 ,
• Ann Robertson 2 ,
• Guro Huby 3 ,
• Anthony Avery 1 &
• Aziz Sheikh 2  

BMC Medical Research Methodology volume  11 , Article number:  100 ( 2011 ) Cite this article

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The case study approach allows in-depth, multi-faceted explorations of complex issues in their real-life settings. The value of the case study approach is well recognised in the fields of business, law and policy, but somewhat less so in health services research. Based on our experiences of conducting several health-related case studies, we reflect on the different types of case study design, the specific research questions this approach can help answer, the data sources that tend to be used, and the particular advantages and disadvantages of employing this methodological approach. The paper concludes with key pointers to aid those designing and appraising proposals for conducting case study research, and a checklist to help readers assess the quality of case study reports.

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Introduction

The case study approach is particularly useful to employ when there is a need to obtain an in-depth appreciation of an issue, event or phenomenon of interest, in its natural real-life context. Our aim in writing this piece is to provide insights into when to consider employing this approach and an overview of key methodological considerations in relation to the design, planning, analysis, interpretation and reporting of case studies.

The illustrative 'grand round', 'case report' and 'case series' have a long tradition in clinical practice and research. Presenting detailed critiques, typically of one or more patients, aims to provide insights into aspects of the clinical case and, in doing so, illustrate broader lessons that may be learnt. In research, the conceptually-related case study approach can be used, for example, to describe in detail a patient's episode of care, explore professional attitudes to and experiences of a new policy initiative or service development or more generally to 'investigate contemporary phenomena within its real-life context' [ 1 ]. Based on our experiences of conducting a range of case studies, we reflect on when to consider using this approach, discuss the key steps involved and illustrate, with examples, some of the practical challenges of attaining an in-depth understanding of a 'case' as an integrated whole. In keeping with previously published work, we acknowledge the importance of theory to underpin the design, selection, conduct and interpretation of case studies[ 2 ]. In so doing, we make passing reference to the different epistemological approaches used in case study research by key theoreticians and methodologists in this field of enquiry.

This paper is structured around the following main questions: What is a case study? What are case studies used for? How are case studies conducted? What are the potential pitfalls and how can these be avoided? We draw in particular on four of our own recently published examples of case studies (see Tables 1 , 2 , 3 and 4 ) and those of others to illustrate our discussion[ 3 – 7 ].

What is a case study?

A case study is a research approach that is used to generate an in-depth, multi-faceted understanding of a complex issue in its real-life context. It is an established research design that is used extensively in a wide variety of disciplines, particularly in the social sciences. A case study can be defined in a variety of ways (Table 5 ), the central tenet being the need to explore an event or phenomenon in depth and in its natural context. It is for this reason sometimes referred to as a "naturalistic" design; this is in contrast to an "experimental" design (such as a randomised controlled trial) in which the investigator seeks to exert control over and manipulate the variable(s) of interest.

Stake's work has been particularly influential in defining the case study approach to scientific enquiry. He has helpfully characterised three main types of case study: intrinsic , instrumental and collective [ 8 ]. An intrinsic case study is typically undertaken to learn about a unique phenomenon. The researcher should define the uniqueness of the phenomenon, which distinguishes it from all others. In contrast, the instrumental case study uses a particular case (some of which may be better than others) to gain a broader appreciation of an issue or phenomenon. The collective case study involves studying multiple cases simultaneously or sequentially in an attempt to generate a still broader appreciation of a particular issue.

These are however not necessarily mutually exclusive categories. In the first of our examples (Table 1 ), we undertook an intrinsic case study to investigate the issue of recruitment of minority ethnic people into the specific context of asthma research studies, but it developed into a instrumental case study through seeking to understand the issue of recruitment of these marginalised populations more generally, generating a number of the findings that are potentially transferable to other disease contexts[ 3 ]. In contrast, the other three examples (see Tables 2 , 3 and 4 ) employed collective case study designs to study the introduction of workforce reconfiguration in primary care, the implementation of electronic health records into hospitals, and to understand the ways in which healthcare students learn about patient safety considerations[ 4 – 6 ]. Although our study focusing on the introduction of General Practitioners with Specialist Interests (Table 2 ) was explicitly collective in design (four contrasting primary care organisations were studied), is was also instrumental in that this particular professional group was studied as an exemplar of the more general phenomenon of workforce redesign[ 4 ].

What are case studies used for?

According to Yin, case studies can be used to explain, describe or explore events or phenomena in the everyday contexts in which they occur[ 1 ]. These can, for example, help to understand and explain causal links and pathways resulting from a new policy initiative or service development (see Tables 2 and 3 , for example)[ 1 ]. In contrast to experimental designs, which seek to test a specific hypothesis through deliberately manipulating the environment (like, for example, in a randomised controlled trial giving a new drug to randomly selected individuals and then comparing outcomes with controls),[ 9 ] the case study approach lends itself well to capturing information on more explanatory ' how ', 'what' and ' why ' questions, such as ' how is the intervention being implemented and received on the ground?'. The case study approach can offer additional insights into what gaps exist in its delivery or why one implementation strategy might be chosen over another. This in turn can help develop or refine theory, as shown in our study of the teaching of patient safety in undergraduate curricula (Table 4 )[ 6 , 10 ]. Key questions to consider when selecting the most appropriate study design are whether it is desirable or indeed possible to undertake a formal experimental investigation in which individuals and/or organisations are allocated to an intervention or control arm? Or whether the wish is to obtain a more naturalistic understanding of an issue? The former is ideally studied using a controlled experimental design, whereas the latter is more appropriately studied using a case study design.

Case studies may be approached in different ways depending on the epistemological standpoint of the researcher, that is, whether they take a critical (questioning one's own and others' assumptions), interpretivist (trying to understand individual and shared social meanings) or positivist approach (orientating towards the criteria of natural sciences, such as focusing on generalisability considerations) (Table 6 ). Whilst such a schema can be conceptually helpful, it may be appropriate to draw on more than one approach in any case study, particularly in the context of conducting health services research. Doolin has, for example, noted that in the context of undertaking interpretative case studies, researchers can usefully draw on a critical, reflective perspective which seeks to take into account the wider social and political environment that has shaped the case[ 11 ].

How are case studies conducted?

Here, we focus on the main stages of research activity when planning and undertaking a case study; the crucial stages are: defining the case; selecting the case(s); collecting and analysing the data; interpreting data; and reporting the findings.

Defining the case

Carefully formulated research question(s), informed by the existing literature and a prior appreciation of the theoretical issues and setting(s), are all important in appropriately and succinctly defining the case[ 8 , 12 ]. Crucially, each case should have a pre-defined boundary which clarifies the nature and time period covered by the case study (i.e. its scope, beginning and end), the relevant social group, organisation or geographical area of interest to the investigator, the types of evidence to be collected, and the priorities for data collection and analysis (see Table 7 )[ 1 ]. A theory driven approach to defining the case may help generate knowledge that is potentially transferable to a range of clinical contexts and behaviours; using theory is also likely to result in a more informed appreciation of, for example, how and why interventions have succeeded or failed[ 13 ].

For example, in our evaluation of the introduction of electronic health records in English hospitals (Table 3 ), we defined our cases as the NHS Trusts that were receiving the new technology[ 5 ]. Our focus was on how the technology was being implemented. However, if the primary research interest had been on the social and organisational dimensions of implementation, we might have defined our case differently as a grouping of healthcare professionals (e.g. doctors and/or nurses). The precise beginning and end of the case may however prove difficult to define. Pursuing this same example, when does the process of implementation and adoption of an electronic health record system really begin or end? Such judgements will inevitably be influenced by a range of factors, including the research question, theory of interest, the scope and richness of the gathered data and the resources available to the research team.

Selecting the case(s)

The decision on how to select the case(s) to study is a very important one that merits some reflection. In an intrinsic case study, the case is selected on its own merits[ 8 ]. The case is selected not because it is representative of other cases, but because of its uniqueness, which is of genuine interest to the researchers. This was, for example, the case in our study of the recruitment of minority ethnic participants into asthma research (Table 1 ) as our earlier work had demonstrated the marginalisation of minority ethnic people with asthma, despite evidence of disproportionate asthma morbidity[ 14 , 15 ]. In another example of an intrinsic case study, Hellstrom et al.[ 16 ] studied an elderly married couple living with dementia to explore how dementia had impacted on their understanding of home, their everyday life and their relationships.

For an instrumental case study, selecting a "typical" case can work well[ 8 ]. In contrast to the intrinsic case study, the particular case which is chosen is of less importance than selecting a case that allows the researcher to investigate an issue or phenomenon. For example, in order to gain an understanding of doctors' responses to health policy initiatives, Som undertook an instrumental case study interviewing clinicians who had a range of responsibilities for clinical governance in one NHS acute hospital trust[ 17 ]. Sampling a "deviant" or "atypical" case may however prove even more informative, potentially enabling the researcher to identify causal processes, generate hypotheses and develop theory.

In collective or multiple case studies, a number of cases are carefully selected. This offers the advantage of allowing comparisons to be made across several cases and/or replication. Choosing a "typical" case may enable the findings to be generalised to theory (i.e. analytical generalisation) or to test theory by replicating the findings in a second or even a third case (i.e. replication logic)[ 1 ]. Yin suggests two or three literal replications (i.e. predicting similar results) if the theory is straightforward and five or more if the theory is more subtle. However, critics might argue that selecting 'cases' in this way is insufficiently reflexive and ill-suited to the complexities of contemporary healthcare organisations.

The selected case study site(s) should allow the research team access to the group of individuals, the organisation, the processes or whatever else constitutes the chosen unit of analysis for the study. Access is therefore a central consideration; the researcher needs to come to know the case study site(s) well and to work cooperatively with them. Selected cases need to be not only interesting but also hospitable to the inquiry [ 8 ] if they are to be informative and answer the research question(s). Case study sites may also be pre-selected for the researcher, with decisions being influenced by key stakeholders. For example, our selection of case study sites in the evaluation of the implementation and adoption of electronic health record systems (see Table 3 ) was heavily influenced by NHS Connecting for Health, the government agency that was responsible for overseeing the National Programme for Information Technology (NPfIT)[ 5 ]. This prominent stakeholder had already selected the NHS sites (through a competitive bidding process) to be early adopters of the electronic health record systems and had negotiated contracts that detailed the deployment timelines.

It is also important to consider in advance the likely burden and risks associated with participation for those who (or the site(s) which) comprise the case study. Of particular importance is the obligation for the researcher to think through the ethical implications of the study (e.g. the risk of inadvertently breaching anonymity or confidentiality) and to ensure that potential participants/participating sites are provided with sufficient information to make an informed choice about joining the study. The outcome of providing this information might be that the emotive burden associated with participation, or the organisational disruption associated with supporting the fieldwork, is considered so high that the individuals or sites decide against participation.

In our example of evaluating implementations of electronic health record systems, given the restricted number of early adopter sites available to us, we sought purposively to select a diverse range of implementation cases among those that were available[ 5 ]. We chose a mixture of teaching, non-teaching and Foundation Trust hospitals, and examples of each of the three electronic health record systems procured centrally by the NPfIT. At one recruited site, it quickly became apparent that access was problematic because of competing demands on that organisation. Recognising the importance of full access and co-operative working for generating rich data, the research team decided not to pursue work at that site and instead to focus on other recruited sites.

Collecting the data

In order to develop a thorough understanding of the case, the case study approach usually involves the collection of multiple sources of evidence, using a range of quantitative (e.g. questionnaires, audits and analysis of routinely collected healthcare data) and more commonly qualitative techniques (e.g. interviews, focus groups and observations). The use of multiple sources of data (data triangulation) has been advocated as a way of increasing the internal validity of a study (i.e. the extent to which the method is appropriate to answer the research question)[ 8 , 18 – 21 ]. An underlying assumption is that data collected in different ways should lead to similar conclusions, and approaching the same issue from different angles can help develop a holistic picture of the phenomenon (Table 2 )[ 4 ].

Brazier and colleagues used a mixed-methods case study approach to investigate the impact of a cancer care programme[ 22 ]. Here, quantitative measures were collected with questionnaires before, and five months after, the start of the intervention which did not yield any statistically significant results. Qualitative interviews with patients however helped provide an insight into potentially beneficial process-related aspects of the programme, such as greater, perceived patient involvement in care. The authors reported how this case study approach provided a number of contextual factors likely to influence the effectiveness of the intervention and which were not likely to have been obtained from quantitative methods alone.

In collective or multiple case studies, data collection needs to be flexible enough to allow a detailed description of each individual case to be developed (e.g. the nature of different cancer care programmes), before considering the emerging similarities and differences in cross-case comparisons (e.g. to explore why one programme is more effective than another). It is important that data sources from different cases are, where possible, broadly comparable for this purpose even though they may vary in nature and depth.

Analysing, interpreting and reporting case studies

Making sense and offering a coherent interpretation of the typically disparate sources of data (whether qualitative alone or together with quantitative) is far from straightforward. Repeated reviewing and sorting of the voluminous and detail-rich data are integral to the process of analysis. In collective case studies, it is helpful to analyse data relating to the individual component cases first, before making comparisons across cases. Attention needs to be paid to variations within each case and, where relevant, the relationship between different causes, effects and outcomes[ 23 ]. Data will need to be organised and coded to allow the key issues, both derived from the literature and emerging from the dataset, to be easily retrieved at a later stage. An initial coding frame can help capture these issues and can be applied systematically to the whole dataset with the aid of a qualitative data analysis software package.

The Framework approach is a practical approach, comprising of five stages (familiarisation; identifying a thematic framework; indexing; charting; mapping and interpretation) , to managing and analysing large datasets particularly if time is limited, as was the case in our study of recruitment of South Asians into asthma research (Table 1 )[ 3 , 24 ]. Theoretical frameworks may also play an important role in integrating different sources of data and examining emerging themes. For example, we drew on a socio-technical framework to help explain the connections between different elements - technology; people; and the organisational settings within which they worked - in our study of the introduction of electronic health record systems (Table 3 )[ 5 ]. Our study of patient safety in undergraduate curricula drew on an evaluation-based approach to design and analysis, which emphasised the importance of the academic, organisational and practice contexts through which students learn (Table 4 )[ 6 ].

Case study findings can have implications both for theory development and theory testing. They may establish, strengthen or weaken historical explanations of a case and, in certain circumstances, allow theoretical (as opposed to statistical) generalisation beyond the particular cases studied[ 12 ]. These theoretical lenses should not, however, constitute a strait-jacket and the cases should not be "forced to fit" the particular theoretical framework that is being employed.

When reporting findings, it is important to provide the reader with enough contextual information to understand the processes that were followed and how the conclusions were reached. In a collective case study, researchers may choose to present the findings from individual cases separately before amalgamating across cases. Care must be taken to ensure the anonymity of both case sites and individual participants (if agreed in advance) by allocating appropriate codes or withholding descriptors. In the example given in Table 3 , we decided against providing detailed information on the NHS sites and individual participants in order to avoid the risk of inadvertent disclosure of identities[ 5 , 25 ].

What are the potential pitfalls and how can these be avoided?

The case study approach is, as with all research, not without its limitations. When investigating the formal and informal ways undergraduate students learn about patient safety (Table 4 ), for example, we rapidly accumulated a large quantity of data. The volume of data, together with the time restrictions in place, impacted on the depth of analysis that was possible within the available resources. This highlights a more general point of the importance of avoiding the temptation to collect as much data as possible; adequate time also needs to be set aside for data analysis and interpretation of what are often highly complex datasets.

Case study research has sometimes been criticised for lacking scientific rigour and providing little basis for generalisation (i.e. producing findings that may be transferable to other settings)[ 1 ]. There are several ways to address these concerns, including: the use of theoretical sampling (i.e. drawing on a particular conceptual framework); respondent validation (i.e. participants checking emerging findings and the researcher's interpretation, and providing an opinion as to whether they feel these are accurate); and transparency throughout the research process (see Table 8 )[ 8 , 18 – 21 , 23 , 26 ]. Transparency can be achieved by describing in detail the steps involved in case selection, data collection, the reasons for the particular methods chosen, and the researcher's background and level of involvement (i.e. being explicit about how the researcher has influenced data collection and interpretation). Seeking potential, alternative explanations, and being explicit about how interpretations and conclusions were reached, help readers to judge the trustworthiness of the case study report. Stake provides a critique checklist for a case study report (Table 9 )[ 8 ].

Conclusions

The case study approach allows, amongst other things, critical events, interventions, policy developments and programme-based service reforms to be studied in detail in a real-life context. It should therefore be considered when an experimental design is either inappropriate to answer the research questions posed or impossible to undertake. Considering the frequency with which implementations of innovations are now taking place in healthcare settings and how well the case study approach lends itself to in-depth, complex health service research, we believe this approach should be more widely considered by researchers. Though inherently challenging, the research case study can, if carefully conceptualised and thoughtfully undertaken and reported, yield powerful insights into many important aspects of health and healthcare delivery.

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Acknowledgements

We are grateful to the participants and colleagues who contributed to the individual case studies that we have drawn on. This work received no direct funding, but it has been informed by projects funded by Asthma UK, the NHS Service Delivery Organisation, NHS Connecting for Health Evaluation Programme, and Patient Safety Research Portfolio. We would also like to thank the expert reviewers for their insightful and constructive feedback. Our thanks are also due to Dr. Allison Worth who commented on an earlier draft of this manuscript.

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Association of area- and volumetric-mammographic density and breast cancer risk in women of Asian descent: a case control study

• Shivaani Mariapun 1 , 2 ,
• Weang-Kee Ho 1 , 2 ,
• Mikael Eriksson 3 , 9 ,
• Nur Aishah Mohd Taib 4 , 5 ,
• Cheng-Har Yip 5 , 6 ,
• Kartini Rahmat 4 , 7 ,
• Per Hall 3 , 8 &
• Soo-Hwang Teo 1 , 4  

Breast Cancer Research volume  26 , Article number:  79 ( 2024 ) Cite this article

Metrics details

Mammographic density (MD) has been shown to be a strong and independent risk factor for breast cancer in women of European and Asian descent. However, the majority of Asian studies to date have used BI-RADS as the scoring method and none have evaluated area and volumetric densities in the same cohort of women. This study aims to compare the association of MD measured by two automated methods with the risk of breast cancer in Asian women, and to investigate if the association is different for premenopausal and postmenopausal women.

In this case–control study of 531 cases and 2297 controls, we evaluated the association of area-based MD measures and volumetric-based MD measures with breast cancer risk in Asian women using conditional logistic regression analysis, adjusting for relevant confounders. The corresponding association by menopausal status were assessed using unconditional logistic regression.

We found that both area and volume-based MD measures were associated with breast cancer risk. Strongest associations were observed for percent densities (OR (95% CI) was 2.06 (1.42–2.99) for percent dense area and 2.21 (1.44–3.39) for percent dense volume, comparing women in highest density quartile with those in the lowest quartile). The corresponding associations were significant in postmenopausal but not premenopausal women (premenopausal versus postmenopausal were 1.59 (0.95–2.67) and 1.89 (1.22–2.96) for percent dense area and 1.24 (0.70–2.22) and 1.96 (1.19–3.27) for percent dense volume). However, the odds ratios were not statistically different by menopausal status [ p difference = 0.782 for percent dense area and 0.486 for percent dense volume].

Conclusions

This study confirms the associations of mammographic density measured by both area and volumetric methods and breast cancer risk in Asian women. Stronger associations were observed for percent dense area and percent dense volume, and strongest effects were seen in postmenopausal individuals.

Mammographic density (MD) reflects the composition of fibro-glandular tissue of the breast, as visualised on a mammogram. MD is an independent predictor of breast cancer risk, although the strength of its association varies across studies, due in part to the different methods of MD assessment and different partitioning thresholds used to define high and low MD [ 1 , 2 , 3 ]. Efforts to make measuring MD less reader-dependent and more reproducible have resulted in the development of a number of fully-automated methods for measuring MD [ 4 , 5 , 6 ], including both volumetric and area-based assessments methods.

In women of European ancestry Volumetric assessments of density have been shown to be a stronger predictor of risk compared to area-based density [ 7 , 8 ]. Volumetric methods are less influenced by compression force and are more sensitive to breast thickness, and may more accurately estimate the amount of fibroglandular tissue for women with larger breasts [ 9 , 10 , 11 ]. However Asian women have smaller and denser breasts compared to women of European ancestry, and the performance of area and volume-based densities have hitherto not been compared in the same study.

In this study, we aim to determine and compare the effects of two automated MD measures, namely STRATUS measurements of area densities, and Volpara measurements of volumetric densities, on breast cancer risk in the Asian population, and to explore the potential variation by menopausal status.

Study participants, data collection and eligibility criteria

Cases comprised of patients who were recruited sequentially into the Malaysian Breast Cancer Genetics (MyBrCa) study from Subang Jaya Medical Centre (SJMC), between 2012 and 2020, and University Malaya Medical Centre (UMMC), between 2003 and 2020. Controls were women between 40 and 74 years old with no prior history of breast cancer that were recruited into the Malaysian Mammography Study (MyMammo) from the same participating hospitals as cases. The study details have been previously published [ 12 ]. All participants answered a detailed questionnaire which included information on lifestyle and reproductive risk factors, socio-demographic factors, and family history and provided blood sample for genetic testing.

Bilateral full-field digital mammograms (FFDMs) for cases were retrieved from the medical image storage servers retrospectively starting in June 2018 and for controls were collected at recruitment. The bilateral cranio-caudal (CC) and medio-lateral oblique (MLO) views for both raw and processed images, where possible, were retrieved. Cases were excluded from the research study if: (a) digital mammograms were conducted more than 12 months prior to cancer diagnosis, (b) only mammograms ipsilateral to the breast cancer were available. Controls were excluded from the research study if no mammograms were available for analysis. All participants included in the study were of self-declared Chinese, Malay or Indian ethnicity and had information on age at mammography, body mass index (BMI) and/or menopausal status. In total, 10% of cases and 69% of controls were available and eligible for matching.

For the case–control analysis of mammographic density and breast cancer risk, as raw and processed images were not available for all women, cases and controls in the full dataset were matched for age (within 5 years) and ethnicity (exact) separately for the analyses of STRATUS, which measures processed images, and Volpara, which measures raw images. Age-matching was performed in each ethnic group using a 1:4 case to control ratio nearest neighbour propensity score matching using the matchit package in R . For the STRATUS study, a total of 488 cases and 1796 controls were included in the matched case–control study, of which 82.2% of cases were matched to four controls, 9% to three controls, 3.5% to two controls and 5.3% to only one control. For the Volpara study, a total of 436 cases and 1623 controls were included, of which 81.4% were matched to four controls, 12.4% to three controls, 3.2% to two controls and 3% to only one control. In total, 531 cases and 2297 controls were included for analysis of which data was available for both STRATUS and Volpara in 393 cases and 1122 controls.

Mammographic density (MD) assessments

Mammography was performed using machines from three different manufacturers; Hologic [Models: Lorad Selenia, Selenia Dimensions and Tomo Selenia Dimensions], General Electric (GE) Senographe Essential, and Siemens Mammomat Novation. Area-based MD was determined using STRATUS, a fully automated machine-learning method for assessing MD based on image features assessed using thresholding methods, by the developers of STRATUS at the Karolinska Institute, Sweden [ 4 ]. Volumetric MD was computed using Volpara Data Manager version 1.1.109 [ 5 ]. Six MD phenotypes were considered in this study: absolute dense area (DA) and volume (DV), percent dense area (PDA, i.e., absolute dense area/total breast area) and volume (PDV, i.e., absolute dense volume/total breast volume), and non-dense area (NDA) and volume (NDV). We also categorised MD according to the computer-generated BI-RADS scores (cBIRADS) generated by STRATUS, and the clinical classification score (Volpara Density Grades (VDG)).

Image laterality

Pearson’s correlation coefficients and previous studies showed that there were strong correlations between CC and MLO measurements [ 13 , 14 ]. The Wilcoxon rank sum test was performed to compare the distribution of MD in the left and right mammograms in the control group. For the CC view mammograms, percent dense volume was higher in the right breast (Left median 9.1%; Right 9.5%, P  = 0.035), whereas for the MLO view, three measures were higher in the left breast [dense volume (Left 57.6 cm 3 ; Right 56.5 cm 3 , P  = 0.006), non-dense volume (Left 591.8 cm 3 ; Right 561.7 cm 3 , P  = 0.011) and total breast volume (Left 653.4 cm 3 ; Right 628.0 cm 3 , P  = 0.006)]. As there was less variation in MD measurements for the CC view, MD measurements from the CC view mammograms of unaffected breasts of cases were used in all analyses, and matched by laterality in the controls.

Statistical analyses

Box-Cox transformation was used to transform MD phenotypes into approximately normal distribution.

Confounder selection

Covariates that were assessed include socio-demographic factors, known lifestyle and reproductive risk factors of breast cancer, mammogram machine and compressed breast thickness. A covariate was considered confounding if: (a) it was significantly associated with MD in controls at P  < 0.05, after accounting for other associated variables; (b) it was significantly associated with breast cancer risk at P  < 0.05, after accounting for other associated variables; and (c) it had a magnitude of confounding that was greater than 5%.

Age at first full term pregnancy, total number of live births and breast feeding were only evaluated among parous women. Parous women were defined as those who have had at least one full-term pregnancy. The use of hormone replacement therapy (HRT) was only evaluated among postmenopausal women. Postmenopausal women were defined as women who have not had their periods for at least 12 months prior to their enrolment into the study or if they self-reported that they were postmenopausal at enrolment.

Association of mammographic density (MD) phenotypes and breast cancer risk

We assessed the association between mammographic density phenotypes (treated either as continuous or categorical variables) and breast cancer risk using conditional logistic regression, adjusting for selected confounders. When MD was treated as a continuous variable, odds ratios per-adjusted standard deviations (OPERA [ 15 ]) was calculated to allow comparison across MD phenotypes. When MD was treated as a categorical variable, MD phenotypes were categorised into four equal quartiles based on the MD distribution in controls, using the first quartile as the reference group. We also categorised MD according to the computer-generated BI-RADS scores, cBIRADS, generated by STRATUS, and Volpara Density Grades (VDG), which is the classification used to report density, measured by Volpara, in the clinic. Weighted kappa, using quadratic weighting, was calculated to assess the concordance between quantiles of STRATUS and Volpara measurements.

The association between MD phenotypes and breast cancer risk by menopausal status were conducted using unconditional regression. Z-tests were conducted to determine whether the odds ratios for mammographic densities and breast cancer risk were different for premenopausal and postmenopausal women.

All statistical analyses were performed with R version 3.6.1.

Characteristics of study participants

Participant selection and descriptive statistics of cases and controls are presented in Fig.  1 and Table  1 . The majority of controls within the STRATUS study (67.7%) were recruited from the private tertiary hospital (SJMC), while approximately half of the controls within the Volpara study were from the government-funded teaching hospital (UMMC). Most of the mammograms were obtained from the Hologic machine.

Flowchart illustrating a the selection of cases and controls for mammographic density (MD) assessment by STRATUS and Volpara, and b participants included in the different analyses performed including the analysis of (1) the association of covariates with MD, (2) the association of covariates with breast cancer risk, and (3) the association of MD and breast cancer risk

Confounders

We identified potential confounders as covariates with P value < 0.05 with both MD phenotypes and breast cancer risk in the multivariable models, and these were breastfeeding for absolute dense area and dense volume, alcohol intake for non-dense volume and breast thickness for all MD phenotypes except dense area (Additional file 1 : Table S1). Additionally, although not significant in our study, menopausal status and parity were included as potential confounders as these variables have consistently been reported to be associated with both MD and breast cancer risk in the literature. Of the list of potential confounders, only those resulting in > 5% change in the magnitude of MD association with risk were retained in the model for adjustment. The final list of variables included in the association analyses for adjustment can be found Additional file 1 : Table S2.

When treated as a continuous variable, both dense area and dense volume were significantly associated with breast cancer risk, the odds per adjusted standard deviation (OPERA) and the corresponding 95% CI were 1.19 (1.08–1.32) and 1.14 (1.02–1.28), respectively (Fig.  2 ). However, when categorised into quartiles, only the highest quartile of dense area was significantly associated with risk (odds ratio (95% CI) was 1.44 (1.03–1.21)). This association was no longer significant in analyses limited to overlapping samples between the STRATUS and Volpara studies (1.26, 95% CI: 0.83-1.91) (Fig.  3 ).

Associations of a STRATUS area mammographic densities and b Volpara volumetric mammographic densities, with breast cancer risk. *Adjusted for relevant confounding factors. † Z-tests comparing estimated regression coefficients between the STRATUS and Volpara studies

Associations of a STRATUS area mammographic densities, b Volpara volumetric mammographic densities, with breast cancer risk in the dataset of 393 cases and 1122 controls included in both STRATUS and Volpara studies. *Adjusted for relevant confounding factors. † Z-tests comparing estimated regression coefficients between the STRATUS and Volpara studies

For percent density, OPERA for percent dense area was significant (1.23, 95% CI 1.10–1.37) while the OPERA for percent dense volume was not significant (1.08, 95% CI 0.97–1.20). However, quartiles analyses of percent density showed significant association for both MD measurement methods, with risk estimates increased consistently across quartiles. The OR of highest versus lowest quartile was 2.06 (95% CI 1.42–2.99) for percent dense area and 2.21 (95% CI 1.44–3.39) for percent dense volume (Fig.  2 ). There was no significant difference between the ORs of percent dense area and percent dense volume (p-value of Z-test < 0.05). Similar results were observed for analyses limited to overlapping samples between the STRATUS and Volpara studies (Fig.  3 ).

Non-dense area was significantly associated with a lower breast cancer risk (OPERA 0.85, 95% CI 0.76–0.95). Risk estimates decreased consistently, from OR 0.62 (95% CI: 0.45-0.86) to 0.50 (95% CI: 0.35-0.71) and 0.30 (95% CI: 0.19-0.47), comparing the first quartile of non-dense area with the second, third and fourth quartile, respectively. By contrast, the OPERA estimate for non-dense volume was not significant (1.06, 95% CI: 0.95-1.19), although the pattern of association for quartiles was similar to that observed for non-dense area i.e., OR 0.87 (95% CI: 0.61-1.24), OR 0.66 (95% CI: 0.42-1.01) and OR 0.54 (95% CI: 0.31-0.94) for the second, third and fourth quartiles respectively, the corresponding strengths of association were weaker (Figs.  2 and 3 ).

Where densities were categorised according to area-based cBIRADS and volume-based VDG, women in cBIRADS 3 and cBIRADS 4 were associated with a 2.5-fold ( P  = 0.003) and 2.9-fold ( P  < 0.001) greater odds of disease, respectively (Fig.  2 a). By contrast, VDG was not associated with breast cancer risk (Fig.  2 b). The same pattern was observed for analyses limited to overlapping samples between the STRATUS and Volpara studies (Fig.  3 ).

There are no appreciable differences between the results generated using the CC and MLO view measurements (Additional file 1 : Table S2).

The agreement between the STRATUS and Volpara measurements for classifying women into mammographic density quartiles was fair for absolute density (Weighted Kappa, κw = 0.28) and percent density (0.35), and moderate for non-dense area and volume (0.50). Figure  4 illustrates the magnitude of concordance for the classification of area and volumetric MD quartiles. Although there is some agreement between STRATUS and Volpara, there are instances of discordance where individuals shift to adjacent quartiles or even skip one quartile altogether.

Concordance between the classification of a absolute dense area/volume, b percent dense area/volume and c non-dense area/volume into quartiles using STRATUS and Volpara measurements. Note: Agreement between the STRATUS and Volpara measurements for classifying women into mammographic density quartiles was calculated using Cohen’s weighted kappa. Weighted Kappa, κw values for dense area/volume, percent dense area/volume, and non-dense area/volume were 0.28, 0.35 and 0.50, respectively

Analyses by menopausal status

Figures  5 and 6 show the association of MD with breast cancer risk for premenopausal and postmenopausal women, respectively. For dense area and dense volume, both OPERAs and quantile analyses were not significantly associated with breast cancer risk in premenopausal women. By contrast, consistent with the all-women analysis, OPERA for both dense area (OR 1.23, 95% CI: 1.07–1.41) and dense volume (OR 1.30, 95% CI: 1.10–1.54) were significant in postmenopausal women, but the corresponding quartile analyses did not show significant associations for dense area and was only significant for the association of the highest dense volume quartile and risk when compared to the lowest dense volume quartile among postmenopausal women (OR 1.65, 95% CI: 1.01-2.71).

Associations of a STRATUS area mammographic densities and b Volpara volumetric mammographic densities, with breast cancer risk in premenopausal women. *Adjusted for relevant confounding factors. † Reference category is cBIRADS 1 (< 2%) + cBIRADS 2 (2− < 17%). ‡ Reference category is VDG 1 (< 4.8%) + VDG 2 (4.8—< 8.0%). § Z-tests comparing estimated regression coefficients between the STRATUS and Volpara studies

Associations of a STRATUS area mammographic densities, b Volpara volumetric mammographic densities, with breast cancer risk in postmenopausal women and, c comparison of regression coefficients for premenopausal and postmenopausal women. *Adjusted for relevant confounding factors. † Z-tests comparing estimated regression coefficients between the STRATUS and Volpara studies. ‡ Z-tests comparing estimated regression coefficients between premenopausal and postmenopausal women

For percent density, OPERAs for percent dense area and percent dense volume were significant in postmenopausal women but not premenopausal women. The OPERAs were 1.23 (95% CI 1.07–1.41) and 1.16 (95% CI 1.01–1.34) for precent dense area and percent dense volume, respectively, in postmenopausal women. The corresponding estimates in premenopausal women were 1.16 (95% CI 0.99–1.35) and 1.01 (95% CI 0.86–1.19). The observed significant association of highest versus lowest quartile in all women analysis was replicated in postmenopausal women (OR 1.89, 95% CI: 1.22-2.96 for percent dense area; OR 1.96, 95% CI: 1.19-3.27 for percent dense volume), but not premenopausal women (OR 1.59, 95% CI: 0.95-2.67 for percent dense area; OR 1.24, 95% CI: 0.70-2.22 for percent dense volume).

For non-dense MD phenotype in both premenopausal and postmenopausal women, OPERAs were not significant in both non-dense area (0.88, 95% CI: 0.75-1.02 and 0.87, 95% CI: 0.75-1.01 for premenopausal and postmenopausal women, respectively) and non-dense volume (1.11, 95% CI: 0.95-1.31 and 1.00, 95% CI: 0.85-1.18, respectively) measurements. However, the quartile analyses for both non-dense area and non-dense volume were significant in premenopausal women, comparing the highest and lowest non-dense area quartiles (OR 0.37, 95% CI: 0.20-0.66) and non-dense volume quartiles (OR 0.31, 95% CI: 0.14-0.67), but not postmenopausal women (OR 0.60, 95% CI: 0.36-1.01 for non-dense area; OR 0.88, 95% CI: 0.51-1.54 for non-dense volume).

In this study of women of Asian-ancestry, we found that percent mammographic density is a strong breast cancer risk factor, with similar magnitudes of association for both area and volumetric mammographic density measures. Comparing women in the lowest quartiles, women with percent density in the highest quartiles had approximately two-fold higher odds of breast cancer. The observed association was however significant only in postmenopausal women but not in premenopausal women.

The two-fold risk estimates reported in this study are consistent with those found in a meta-analysis of Japanese, Korean and Singaporean women comprising of one cohort study and five case–control studies, which reported a summary effect size of 2.2 (95% CI 1.5–3.2) [ 16 ], as well as with a large meta-analysis of European women using the BI-RADS density four-category classification [ 3 ]. The corresponding odds ratio per adjusted standard deviation (OPERA) was similar to a Korean study of 213 cases and 630 controls [ 17 ], but lower than those previously reported in women of European ancestry. A study of Australian women reported OPERA of 1.52 (95% CI 1.34–1.73) for percent dense area, compared to 1.23 (95% CI 1.10–1.37) this study, suggesting potential ethnic differences in MD-risk associations [ 18 ].

Our findings of lack of MD-risk association in premenopausal women align with similar-sized studies in other Asian populations [ 19 , 20 , 21 , 22 ]. For instance, a multicentre Japanese study (530 cases, 1043 controls) found a near three-fold increase in breast cancer odds (OR 2.9, 95% CI 1.1–7.2) among postmenopausal women with extremely dense breast (>75% glandular tissue), while no significant association was observed in premenopausal women [ 19 ]. Similarly, another study in Japanese women (146 cases, 659 controls) revealed a four-fold higher odds of breast cancer among postmenopausal women with > 75% percent densities, with no significant association in premenopausal women [ 21 ]. However, it is important to note that a recent large prospective Korean study comprising of ~ 65,000 breast cancer cases reported that breast density is associated with breast cancer risk in both premenopausal (OR 2.4, 95% CI 2.2–2.5) and postmenopausal (OR 2.9, 95% CI 2.8–3.0) women, suggesting that larger sample sizes in premenopausal women are required to detect a significant association with breast cancer risk [ 20 ].

Our study did not yield conclusive evidence regarding the association of absolute MD measures with breast cancer risk. While the odds ratios for continuous dense area and dense volume were significant at a nominal level (1.19, 95% CI 1.08–1.32 and 1.14, 95% CI 1.02–1.28, respectively), the results from quartile analysis did not support the significant associations. We also observed a stronger inverse association with non-dense area compared to non-dense volume that was significant in our analyses of all women and premenopausal women, but not that of postmenopausal women. This inverse association is consistent with previous studies in women of European ancestry reporting a protective effect of having greater amounts of fat or non-dense tissue in the breast [ 23 ].

In summary, our study confirms the significance of MD as a robust breast cancer risk factor in Asian-ancestry women, with percent density showing consistent associations across area and volumetric-based measures. However, the lack of MD-risk association in premenopausal women underscores the need for further investigation in larger datasets. While our findings contribute to the understanding of MD and breast cancer risk, the inconclusive evidence regarding absolute MD measures prompts a critical evaluation of their utility in risk prediction models for this population.

This study had several limitations. First, more than 90% of the cases were recruited from one recruitment centre, making it impossible to match cases and controls based on centre. However, we adjusted our analyses for this factor. Second, some covariates have missingness rates greater than 10%, which may explain some of the unexpected results (e.g. the protective effect observed for HRT among postmenopausal women and alcohol consumption). Third, the healthy controls were women attending an opportunistic screening mammography programme and may be enriched for a family history of breast cancer. This is likely to be the reason family history of breast cancer is not associated with breast cancer risk in this study. Finally, only the mammograms performed at the time of cancer detection (or close to cancer detection) were available for the cases. Given that densities measured from the unaffected contralateral breasts have been shown to be similarly associated with risk of disease [ 8 ], densities of the contralateral breasts were used as surrogate measurements.

In conclusion, our study underscores the significance of mammographic density (MD) as a strong predictor of breast cancer risk in women of Asian-ancestry, particularly in postmenopausal individuals. While percent density, for both area- and volume-based measures, consistently demonstrated significant association, absolute MD measures yielded inconclusive results. Future research should aim to elucidate ethnic-specific MD-risk associations and refine risk prediction models to incorporate the most predictive MD measures, thus enabling more targeted preventive strategies for women of Asian ancestry.

Availability of data and materials

Datasets described and analysed in this manuscript are available from the corresponding author on reasonable request.

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Acknowledgements

We want to thank all the study participants, clinicians, and support staff at Subang Jaya Medical Centre and University Malaya Medical Centre for their generous contributions to the Malaysian Mammography Study (MyMammo) and the Malaysian Breast Cancer Genetic Study (MyBrCa) studies. We thank all the research associates, scientists and staff at Cancer Research Malaysia and University of Malaya who were involved in the MyMammo and MyBrCa studies – this work would not have been possible without their support and contributions.

The Malaysian Ministry of Science and the Malaysian Ministry of Higher Education High Impact Research Grant (grant number: UM.C/HIR/MOHE/06) was used to fund the Malaysian Breast Cancer Genetic Study (MyBrCa). Funds raised through the Sime Darby LPGA tournament and from the High Impact Research Grant were used to support the Malaysian Mammography Study (MyMammo). Additional funds were received from Yayasan Sime Darby, PETRONAS, Estee Lauder Group of Companies, and other donors of Cancer Research Malaysia. WKH and SM are recipients of the L’Oreal-UNESCO For Women in Science National Fellowship.

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Department of Surgery, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

Nur Aishah Mohd Taib & Cheng-Har Yip

Subang Jaya Medical Centre, Subang Jaya, Malaysia

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Biomedical Imaging Department, Faculty of Medicine, Universiti Malaya Research Imaging Centre, University of Malaya, Kuala Lumpur, Malaysia

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Department of Oncology, Södersjukhuset, Stockholm, Sweden

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Conceptualization and design: SM, WKH and ST; Data collection: SM, NAMT, CHY, and KR; Data analysis and interpretation: SM, WKH, ME, PH and ST; Manuscript writing: SM, WKH and ST; Reviewed manuscript: SM, WKH, ME, NAMT, CHY, KR, PH and ST.

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The Malaysian Mammography Study (MyMammo) and the Malaysian Breast Cancer Genetics (MyBrCa) studies were approved by the Independent Ethics Committee, Ramsay Sime Darby Health Care (reference numbers 201109.4 and 201208.1) and the Medical Ethics Committee, University Malaya Medical Centre (reference numbers 1030.8 and 842.9). Written informed consent was obtained from all participants.

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The authors declare no nonfinancial conflicts of interest but the following financial conflict interests: Mikael Eriksson and Per Hall report research grants and a patent on system and method for assessing breast cancer risk using imagery with a license to iCAD, Inc.

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Mariapun, S., Ho, WK., Eriksson, M. et al. Association of area- and volumetric-mammographic density and breast cancer risk in women of Asian descent: a case control study. Breast Cancer Res 26 , 79 (2024). https://doi.org/10.1186/s13058-024-01829-2

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A data-driven robust decision-making model for configuring a resilient and responsive relief supply chain under mixed uncertainty

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• Published: 15 May 2024

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• Bahar Javan-Molaei 1 ,
• Reza Tavakkoli-Moghaddam   ORCID: orcid.org/0000-0002-6757-926X 2 , 3 ,
• Mohssen Ghanavati-Nejad 1 &
• Amin Asghari-Asl 4  

The crucial role of the Relief Supply Chains (RSCs) in the response phase of disaster management is undeniable. However, the literature shows that the simultaneous consideration of the resilience and responsiveness dimensions in designing the RSCs under mixed uncertainty has been ignored by researchers. In this regard, to cover the mentioned gap, the current study aims to configure an RSC by considering two critically important features namely resilience and responsiveness under mixed uncertainty. For this purpose, this work proposed a multi-stage Decision-Making Framework (DMF). In the first stage, a Multi-Objective Model (MOM) is proposed that minimizes the total cost, maximizes the responsiveness level, and maximizes the resilience of the RSC. In the second stage, to deal with mixed uncertainty, a data-driven robust approach based on the Fuzzy Robust Stochastic (FRS), Seasonal Auto-Regressive Integrated Moving Average Exogenous (SARIMAX), and Artificial Neural Networks (ANN) methods is developed. In the third stage, to solve the proposed model, a novel variant of the goal programming method is developed. In general, the main contribution of this study is to develop a novel data-driven DMF to design a resilient-responsive RSC. To show the applicability and efficiency of the developed decision-making method, a real-world case study, the flood that happened in 2019 in Golestan province, Iran, is considered. Eventually, sensitivity analysis, managerial insights, and theoretical implications are presented. According to the achieved results, primary suppliers 1, 3, 5, and 7 and also backup supplier 1 are selected. Also, the results demonstrate that distribution centers 1, 2, 3, and 5 are established. Moreover, the optimal utilization of different transportation modes is specified in the achieved results. The outputs demonstrate that the developed data-driven FRS approach has better performance in comparison with the deterministic and traditional FRS models. Besides, the outputs indicate that the developed solution method has better performance in comparison with the traditional approaches.

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Javan-Molaei, B., Tavakkoli-Moghaddam, R., Ghanavati-Nejad, M. et al. A data-driven robust decision-making model for configuring a resilient and responsive relief supply chain under mixed uncertainty. Ann Oper Res (2024). https://doi.org/10.1007/s10479-024-06038-w

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Methodology or method? A critical review of qualitative case study reports

Despite on-going debate about credibility, and reported limitations in comparison to other approaches, case study is an increasingly popular approach among qualitative researchers. We critically analysed the methodological descriptions of published case studies. Three high-impact qualitative methods journals were searched to locate case studies published in the past 5 years; 34 were selected for analysis. Articles were categorized as health and health services ( n= 12), social sciences and anthropology ( n= 7), or methods ( n= 15) case studies. The articles were reviewed using an adapted version of established criteria to determine whether adequate methodological justification was present, and if study aims, methods, and reported findings were consistent with a qualitative case study approach. Findings were grouped into five themes outlining key methodological issues: case study methodology or method, case of something particular and case selection, contextually bound case study, researcher and case interactions and triangulation, and study design inconsistent with methodology reported. Improved reporting of case studies by qualitative researchers will advance the methodology for the benefit of researchers and practitioners.

Case study research is an increasingly popular approach among qualitative researchers (Thomas, 2011 ). Several prominent authors have contributed to methodological developments, which has increased the popularity of case study approaches across disciplines (Creswell, 2013b ; Denzin & Lincoln, 2011b ; Merriam, 2009 ; Ragin & Becker, 1992 ; Stake, 1995 ; Yin, 2009 ). Current qualitative case study approaches are shaped by paradigm, study design, and selection of methods, and, as a result, case studies in the published literature vary. Differences between published case studies can make it difficult for researchers to define and understand case study as a methodology.

Experienced qualitative researchers have identified case study research as a stand-alone qualitative approach (Denzin & Lincoln, 2011b ). Case study research has a level of flexibility that is not readily offered by other qualitative approaches such as grounded theory or phenomenology. Case studies are designed to suit the case and research question and published case studies demonstrate wide diversity in study design. There are two popular case study approaches in qualitative research. The first, proposed by Stake ( 1995 ) and Merriam ( 2009 ), is situated in a social constructivist paradigm, whereas the second, by Yin ( 2012 ), Flyvbjerg ( 2011 ), and Eisenhardt ( 1989 ), approaches case study from a post-positivist viewpoint. Scholarship from both schools of inquiry has contributed to the popularity of case study and development of theoretical frameworks and principles that characterize the methodology.

The diversity of case studies reported in the published literature, and on-going debates about credibility and the use of case study in qualitative research practice, suggests that differences in perspectives on case study methodology may prevent researchers from developing a mutual understanding of practice and rigour. In addition, discussion about case study limitations has led some authors to query whether case study is indeed a methodology (Luck, Jackson, & Usher, 2006 ; Meyer, 2001 ; Thomas, 2010 ; Tight, 2010 ). Methodological discussion of qualitative case study research is timely, and a review is required to analyse and understand how this methodology is applied in the qualitative research literature. The aims of this study were to review methodological descriptions of published qualitative case studies, to review how the case study methodological approach was applied, and to identify issues that need to be addressed by researchers, editors, and reviewers. An outline of the current definitions of case study and an overview of the issues proposed in the qualitative methodological literature are provided to set the scene for the review.

Definitions of qualitative case study research

Case study research is an investigation and analysis of a single or collective case, intended to capture the complexity of the object of study (Stake, 1995 ). Qualitative case study research, as described by Stake ( 1995 ), draws together “naturalistic, holistic, ethnographic, phenomenological, and biographic research methods” in a bricoleur design, or in his words, “a palette of methods” (Stake, 1995 , pp. xi–xii). Case study methodology maintains deep connections to core values and intentions and is “particularistic, descriptive and heuristic” (Merriam, 2009 , p. 46).

As a study design, case study is defined by interest in individual cases rather than the methods of inquiry used. The selection of methods is informed by researcher and case intuition and makes use of naturally occurring sources of knowledge, such as people or observations of interactions that occur in the physical space (Stake, 1998 ). Thomas ( 2011 ) suggested that “analytical eclecticism” is a defining factor (p. 512). Multiple data collection and analysis methods are adopted to further develop and understand the case, shaped by context and emergent data (Stake, 1995 ). This qualitative approach “explores a real-life, contemporary bounded system (a case ) or multiple bounded systems (cases) over time, through detailed, in-depth data collection involving multiple sources of information … and reports a case description and case themes ” (Creswell, 2013b , p. 97). Case study research has been defined by the unit of analysis, the process of study, and the outcome or end product, all essentially the case (Merriam, 2009 ).

The case is an object to be studied for an identified reason that is peculiar or particular. Classification of the case and case selection procedures informs development of the study design and clarifies the research question. Stake ( 1995 ) proposed three types of cases and study design frameworks. These include the intrinsic case, the instrumental case, and the collective instrumental case. The intrinsic case is used to understand the particulars of a single case, rather than what it represents. An instrumental case study provides insight on an issue or is used to refine theory. The case is selected to advance understanding of the object of interest. A collective refers to an instrumental case which is studied as multiple, nested cases, observed in unison, parallel, or sequential order. More than one case can be simultaneously studied; however, each case study is a concentrated, single inquiry, studied holistically in its own entirety (Stake, 1995 , 1998 ).

Researchers who use case study are urged to seek out what is common and what is particular about the case. This involves careful and in-depth consideration of the nature of the case, historical background, physical setting, and other institutional and political contextual factors (Stake, 1998 ). An interpretive or social constructivist approach to qualitative case study research supports a transactional method of inquiry, where the researcher has a personal interaction with the case. The case is developed in a relationship between the researcher and informants, and presented to engage the reader, inviting them to join in this interaction and in case discovery (Stake, 1995 ). A postpositivist approach to case study involves developing a clear case study protocol with careful consideration of validity and potential bias, which might involve an exploratory or pilot phase, and ensures that all elements of the case are measured and adequately described (Yin, 2009 , 2012 ).

Current methodological issues in qualitative case study research

The future of qualitative research will be influenced and constructed by the way research is conducted, and by what is reviewed and published in academic journals (Morse, 2011 ). If case study research is to further develop as a principal qualitative methodological approach, and make a valued contribution to the field of qualitative inquiry, issues related to methodological credibility must be considered. Researchers are required to demonstrate rigour through adequate descriptions of methodological foundations. Case studies published without sufficient detail for the reader to understand the study design, and without rationale for key methodological decisions, may lead to research being interpreted as lacking in quality or credibility (Hallberg, 2013 ; Morse, 2011 ).

There is a level of artistic license that is embraced by qualitative researchers and distinguishes practice, which nurtures creativity, innovation, and reflexivity (Denzin & Lincoln, 2011b ; Morse, 2009 ). Qualitative research is “inherently multimethod” (Denzin & Lincoln, 2011a , p. 5); however, with this creative freedom, it is important for researchers to provide adequate description for methodological justification (Meyer, 2001 ). This includes paradigm and theoretical perspectives that have influenced study design. Without adequate description, study design might not be understood by the reader, and can appear to be dishonest or inaccurate. Reviewers and readers might be confused by the inconsistent or inappropriate terms used to describe case study research approach and methods, and be distracted from important study findings (Sandelowski, 2000 ). This issue extends beyond case study research, and others have noted inconsistencies in reporting of methodology and method by qualitative researchers. Sandelowski ( 2000 , 2010 ) argued for accurate identification of qualitative description as a research approach. She recommended that the selected methodology should be harmonious with the study design, and be reflected in methods and analysis techniques. Similarly, Webb and Kevern ( 2000 ) uncovered inconsistencies in qualitative nursing research with focus group methods, recommending that methodological procedures must cite seminal authors and be applied with respect to the selected theoretical framework. Incorrect labelling using case study might stem from the flexibility in case study design and non-directional character relative to other approaches (Rosenberg & Yates, 2007 ). Methodological integrity is required in design of qualitative studies, including case study, to ensure study rigour and to enhance credibility of the field (Morse, 2011 ).

Case study has been unnecessarily devalued by comparisons with statistical methods (Eisenhardt, 1989 ; Flyvbjerg, 2006 , 2011 ; Jensen & Rodgers, 2001 ; Piekkari, Welch, & Paavilainen, 2009 ; Tight, 2010 ; Yin, 1999 ). It is reputed to be the “the weak sibling” in comparison to other, more rigorous, approaches (Yin, 2009 , p. xiii). Case study is not an inherently comparative approach to research. The objective is not statistical research, and the aim is not to produce outcomes that are generalizable to all populations (Thomas, 2011 ). Comparisons between case study and statistical research do little to advance this qualitative approach, and fail to recognize its inherent value, which can be better understood from the interpretive or social constructionist viewpoint of other authors (Merriam, 2009 ; Stake, 1995 ). Building on discussions relating to “fuzzy” (Bassey, 2001 ), or naturalistic generalizations (Stake, 1978 ), or transference of concepts and theories (Ayres, Kavanaugh, & Knafl, 2003 ; Morse et al., 2011 ) would have more relevance.

Case study research has been used as a catch-all design to justify or add weight to fundamental qualitative descriptive studies that do not fit with other traditional frameworks (Merriam, 2009 ). A case study has been a “convenient label for our research—when we ‘can't think of anything ‘better”—in an attempt to give it [qualitative methodology] some added respectability” (Tight, 2010 , p. 337). Qualitative case study research is a pliable approach (Merriam, 2009 ; Meyer, 2001 ; Stake, 1995 ), and has been likened to a “curious methodological limbo” (Gerring, 2004 , p. 341) or “paradigmatic bridge” (Luck et al., 2006 , p. 104), that is on the borderline between postpositivist and constructionist interpretations. This has resulted in inconsistency in application, which indicates that flexibility comes with limitations (Meyer, 2001 ), and the open nature of case study research might be off-putting to novice researchers (Thomas, 2011 ). The development of a well-(in)formed theoretical framework to guide a case study should improve consistency, rigour, and trust in studies published in qualitative research journals (Meyer, 2001 ).

Assessment of rigour

The purpose of this study was to analyse the methodological descriptions of case studies published in qualitative methods journals. To do this we needed to develop a suitable framework, which used existing, established criteria for appraising qualitative case study research rigour (Creswell, 2013b ; Merriam, 2009 ; Stake, 1995 ). A number of qualitative authors have developed concepts and criteria that are used to determine whether a study is rigorous (Denzin & Lincoln, 2011b ; Lincoln, 1995 ; Sandelowski & Barroso, 2002 ). The criteria proposed by Stake ( 1995 ) provide a framework for readers and reviewers to make judgements regarding case study quality, and identify key characteristics essential for good methodological rigour. Although each of the factors listed in Stake's criteria could enhance the quality of a qualitative research report, in Table I we present an adapted criteria used in this study, which integrates more recent work by Merriam ( 2009 ) and Creswell ( 2013b ). Stake's ( 1995 ) original criteria were separated into two categories. The first list of general criteria is “relevant for all qualitative research.” The second list, “high relevance to qualitative case study research,” was the criteria that we decided had higher relevance to case study research. This second list was the main criteria used to assess the methodological descriptions of the case studies reviewed. The complete table has been preserved so that the reader can determine how the original criteria were adapted.

Framework for assessing quality in qualitative case study research.

Adapted from Stake ( 1995 , p. 131).

Study design

The critical review method described by Grant and Booth ( 2009 ) was used, which is appropriate for the assessment of research quality, and is used for literature analysis to inform research and practice. This type of review goes beyond the mapping and description of scoping or rapid reviews, to include “analysis and conceptual innovation” (Grant & Booth, 2009 , p. 93). A critical review is used to develop existing, or produce new, hypotheses or models. This is different to systematic reviews that answer clinical questions. It is used to evaluate existing research and competing ideas, to provide a “launch pad” for conceptual development and “subsequent testing” (Grant & Booth, 2009 , p. 93).

Qualitative methods journals were located by a search of the 2011 ISI Journal Citation Reports in Social Science, via the database Web of Knowledge (see m.webofknowledge.com). No “qualitative research methods” category existed in the citation reports; therefore, a search of all categories was performed using the term “qualitative.” In Table II , we present the qualitative methods journals located, ranked by impact factor. The highest ranked journals were selected for searching. We acknowledge that the impact factor ranking system might not be the best measure of journal quality (Cheek, Garnham, & Quan, 2006 ); however, this was the most appropriate and accessible method available.

International Journal of Qualitative Studies on Health and Well-being.

Search strategy

In March 2013, searches of the journals, Qualitative Health Research , Qualitative Research , and Qualitative Inquiry were completed to retrieve studies with “case study” in the abstract field. The search was limited to the past 5 years (1 January 2008 to 1 March 2013). The objective was to locate published qualitative case studies suitable for assessment using the adapted criterion. Viewpoints, commentaries, and other article types were excluded from review. Title and abstracts of the 45 retrieved articles were read by the first author, who identified 34 empirical case studies for review. All authors reviewed the 34 studies to confirm selection and categorization. In Table III , we present the 34 case studies grouped by journal, and categorized by research topic, including health sciences, social sciences and anthropology, and methods research. There was a discrepancy in categorization of one article on pedagogy and a new teaching method published in Qualitative Inquiry (Jorrín-Abellán, Rubia-Avi, Anguita-Martínez, Gómez-Sánchez, & Martínez-Mones, 2008 ). Consensus was to allocate to the methods category.

Outcomes of search of qualitative methods journals.

In Table III , the number of studies located, and final numbers selected for review have been reported. Qualitative Health Research published the most empirical case studies ( n= 16). In the health category, there were 12 case studies of health conditions, health services, and health policy issues, all published in Qualitative Health Research . Seven case studies were categorized as social sciences and anthropology research, which combined case study with biography and ethnography methodologies. All three journals published case studies on methods research to illustrate a data collection or analysis technique, methodological procedure, or related issue.

The methodological descriptions of 34 case studies were critically reviewed using the adapted criteria. All articles reviewed contained a description of study methods; however, the length, amount of detail, and position of the description in the article varied. Few studies provided an accurate description and rationale for using a qualitative case study approach. In the 34 case studies reviewed, three described a theoretical framework informed by Stake ( 1995 ), two by Yin ( 2009 ), and three provided a mixed framework informed by various authors, which might have included both Yin and Stake. Few studies described their case study design, or included a rationale that explained why they excluded or added further procedures, and whether this was to enhance the study design, or to better suit the research question. In 26 of the studies no reference was provided to principal case study authors. From reviewing the description of methods, few authors provided a description or justification of case study methodology that demonstrated how their study was informed by the methodological literature that exists on this approach.

The methodological descriptions of each study were reviewed using the adapted criteria, and the following issues were identified: case study methodology or method; case of something particular and case selection; contextually bound case study; researcher and case interactions and triangulation; and, study design inconsistent with methodology. An outline of how the issues were developed from the critical review is provided, followed by a discussion of how these relate to the current methodological literature.

Case study methodology or method

A third of the case studies reviewed appeared to use a case report method, not case study methodology as described by principal authors (Creswell, 2013b ; Merriam, 2009 ; Stake, 1995 ; Yin, 2009 ). Case studies were identified as a case report because of missing methodological detail and by review of the study aims and purpose. These reports presented data for small samples of no more than three people, places or phenomenon. Four studies, or “case reports” were single cases selected retrospectively from larger studies (Bronken, Kirkevold, Martinsen, & Kvigne, 2012 ; Coltart & Henwood, 2012 ; Hooghe, Neimeyer, & Rober, 2012 ; Roscigno et al., 2012 ). Case reports were not a case of something, instead were a case demonstration or an example presented in a report. These reports presented outcomes, and reported on how the case could be generalized. Descriptions focussed on the phenomena, rather than the case itself, and did not appear to study the case in its entirety.

Case reports had minimal in-text references to case study methodology, and were informed by other qualitative traditions or secondary sources (Adamson & Holloway, 2012 ; Buzzanell & D'Enbeau, 2009 ; Nagar-Ron & Motzafi-Haller, 2011 ). This does not suggest that case study methodology cannot be multimethod, however, methodology should be consistent in design, be clearly described (Meyer, 2001 ; Stake, 1995 ), and maintain focus on the case (Creswell, 2013b ).

To demonstrate how case reports were identified, three examples are provided. The first, Yeh ( 2013 ) described their study as, “the examination of the emergence of vegetarianism in Victorian England serves as a case study to reveal the relationships between boundaries and entities” (p. 306). The findings were a historical case report, which resulted from an ethnographic study of vegetarianism. Cunsolo Willox, Harper, Edge, ‘My Word’: Storytelling and Digital Media Lab, and Rigolet Inuit Community Government (2013) used “a case study that illustrates the usage of digital storytelling within an Inuit community” (p. 130). This case study reported how digital storytelling can be used with indigenous communities as a participatory method to illuminate the benefits of this method for other studies. This “case study was conducted in the Inuit community” but did not include the Inuit community in case analysis (Cunsolo Willox et al., 2013 , p. 130). Bronken et al. ( 2012 ) provided a single case report to demonstrate issues observed in a larger clinical study of aphasia and stroke, without adequate case description or analysis.

Case study of something particular and case selection

Case selection is a precursor to case analysis, which needs to be presented as a convincing argument (Merriam, 2009 ). Descriptions of the case were often not adequate to ascertain why the case was selected, or whether it was a particular exemplar or outlier (Thomas, 2011 ). In a number of case studies in the health and social science categories, it was not explicit whether the case was of something particular, or peculiar to their discipline or field (Adamson & Holloway, 2012 ; Bronken et al., 2012 ; Colón-Emeric et al., 2010 ; Jackson, Botelho, Welch, Joseph, & Tennstedt, 2012 ; Mawn et al., 2010 ; Snyder-Young, 2011 ). There were exceptions in the methods category ( Table III ), where cases were selected by researchers to report on a new or innovative method. The cases emerged through heuristic study, and were reported to be particular, relative to the existing methods literature (Ajodhia-Andrews & Berman, 2009 ; Buckley & Waring, 2013 ; Cunsolo Willox et al., 2013 ; De Haene, Grietens, & Verschueren, 2010 ; Gratton & O'Donnell, 2011 ; Sumsion, 2013 ; Wimpenny & Savin-Baden, 2012 ).

Case selection processes were sometimes insufficient to understand why the case was selected from the global population of cases, or what study of this case would contribute to knowledge as compared with other possible cases (Adamson & Holloway, 2012 ; Bronken et al., 2012 ; Colón-Emeric et al., 2010 ; Jackson et al., 2012 ; Mawn et al., 2010 ). In two studies, local cases were selected (Barone, 2010 ; Fourie & Theron, 2012 ) because the researcher was familiar with and had access to the case. Possible limitations of a convenience sample were not acknowledged. Purposeful sampling was used to recruit participants within the case of one study, but not of the case itself (Gallagher et al., 2013 ). Random sampling was completed for case selection in two studies (Colón-Emeric et al., 2010 ; Jackson et al., 2012 ), which has limited meaning in interpretive qualitative research.

To demonstrate how researchers provided a good justification for the selection of case study approaches, four examples are provided. The first, cases of residential care homes, were selected because of reported occurrences of mistreatment, which included residents being locked in rooms at night (Rytterström, Unosson, & Arman, 2013 ). Roscigno et al. ( 2012 ) selected cases of parents who were admitted for early hospitalization in neonatal intensive care with a threatened preterm delivery before 26 weeks. Hooghe et al. ( 2012 ) used random sampling to select 20 couples that had experienced the death of a child; however, the case study was of one couple and a particular metaphor described only by them. The final example, Coltart and Henwood ( 2012 ), provided a detailed account of how they selected two cases from a sample of 46 fathers based on personal characteristics and beliefs. They described how the analysis of the two cases would contribute to their larger study on first time fathers and parenting.

Contextually bound case study

The limits or boundaries of the case are a defining factor of case study methodology (Merriam, 2009 ; Ragin & Becker, 1992 ; Stake, 1995 ; Yin, 2009 ). Adequate contextual description is required to understand the setting or context in which the case is revealed. In the health category, case studies were used to illustrate a clinical phenomenon or issue such as compliance and health behaviour (Colón-Emeric et al., 2010 ; D'Enbeau, Buzzanell, & Duckworth, 2010 ; Gallagher et al., 2013 ; Hooghe et al., 2012 ; Jackson et al., 2012 ; Roscigno et al., 2012 ). In these case studies, contextual boundaries, such as physical and institutional descriptions, were not sufficient to understand the case as a holistic system, for example, the general practitioner (GP) clinic in Gallagher et al. ( 2013 ), or the nursing home in Colón-Emeric et al. ( 2010 ). Similarly, in the social science and methods categories, attention was paid to some components of the case context, but not others, missing important information required to understand the case as a holistic system (Alexander, Moreira, & Kumar, 2012 ; Buzzanell & D'Enbeau, 2009 ; Nairn & Panelli, 2009 ; Wimpenny & Savin-Baden, 2012 ).

In two studies, vicarious experience or vignettes (Nairn & Panelli, 2009 ) and images (Jorrín-Abellán et al., 2008 ) were effective to support description of context, and might have been a useful addition for other case studies. Missing contextual boundaries suggests that the case might not be adequately defined. Additional information, such as the physical, institutional, political, and community context, would improve understanding of the case (Stake, 1998 ). In Boxes 1 and 2 , we present brief synopses of two studies that were reviewed, which demonstrated a well bounded case. In Box 1 , Ledderer ( 2011 ) used a qualitative case study design informed by Stake's tradition. In Box 2 , Gillard, Witt, and Watts ( 2011 ) were informed by Yin's tradition. By providing a brief outline of the case studies in Boxes 1 and 2 , we demonstrate how effective case boundaries can be constructed and reported, which may be of particular interest to prospective case study researchers.

Article synopsis of case study research using Stake's tradition

Ledderer ( 2011 ) used a qualitative case study research design, informed by modern ethnography. The study is bounded to 10 general practice clinics in Denmark, who had received federal funding to implement preventative care services based on a Motivational Interviewing intervention. The researcher question focussed on “why is it so difficult to create change in medical practice?” (Ledderer, 2011 , p. 27). The study context was adequately described, providing detail on the general practitioner (GP) clinics and relevant political and economic influences. Methodological decisions are described in first person narrative, providing insight on researcher perspectives and interaction with the case. Forty-four interviews were conducted, which focussed on how GPs conducted consultations, and the form, nature and content, rather than asking their opinion or experience (Ledderer, 2011 , p. 30). The duration and intensity of researcher immersion in the case enhanced depth of description and trustworthiness of study findings. Analysis was consistent with Stake's tradition, and the researcher provided examples of inquiry techniques used to challenge assumptions about emerging themes. Several other seminal qualitative works were cited. The themes and typology constructed are rich in narrative data and storytelling by clinic staff, demonstrating individual clinic experiences as well as shared meanings and understandings about changing from a biomedical to psychological approach to preventative health intervention. Conclusions make note of social and cultural meanings and lessons learned, which might not have been uncovered using a different methodology.

Article synopsis of case study research using Yin's tradition

Gillard et al. ( 2011 ) study of camps for adolescents living with HIV/AIDs provided a good example of Yin's interpretive case study approach. The context of the case is bounded by the three summer camps of which the researchers had prior professional involvement. A case study protocol was developed that used multiple methods to gather information at three data collection points coinciding with three youth camps (Teen Forum, Discover Camp, and Camp Strong). Gillard and colleagues followed Yin's ( 2009 ) principles, using a consistent data protocol that enhanced cross-case analysis. Data described the young people, the camp physical environment, camp schedule, objectives and outcomes, and the staff of three youth camps. The findings provided a detailed description of the context, with less detail of individual participants, including insight into researcher's interpretations and methodological decisions throughout the data collection and analysis process. Findings provided the reader with a sense of “being there,” and are discovered through constant comparison of the case with the research issues; the case is the unit of analysis. There is evidence of researcher immersion in the case, and Gillard reports spending significant time in the field in a naturalistic and integrated youth mentor role.

This case study is not intended to have a significant impact on broader health policy, although does have implications for health professionals working with adolescents. Study conclusions will inform future camps for young people with chronic disease, and practitioners are able to compare similarities between this case and their own practice (for knowledge translation). No limitations of this article were reported. Limitations related to publication of this case study were that it was 20 pages long and used three tables to provide sufficient description of the camp and program components, and relationships with the research issue.

Researcher and case interactions and triangulation

Researcher and case interactions and transactions are a defining feature of case study methodology (Stake, 1995 ). Narrative stories, vignettes, and thick description are used to provoke vicarious experience and a sense of being there with the researcher in their interaction with the case. Few of the case studies reviewed provided details of the researcher's relationship with the case, researcher–case interactions, and how these influenced the development of the case study (Buzzanell & D'Enbeau, 2009 ; D'Enbeau et al., 2010 ; Gallagher et al., 2013 ; Gillard et al., 2011 ; Ledderer, 2011 ; Nagar-Ron & Motzafi-Haller, 2011 ). The role and position of the researcher needed to be self-examined and understood by readers, to understand how this influenced interactions with participants, and to determine what triangulation is needed (Merriam, 2009 ; Stake, 1995 ).

Gillard et al. ( 2011 ) provided a good example of triangulation, comparing data sources in a table (p. 1513). Triangulation of sources was used to reveal as much depth as possible in the study by Nagar-Ron and Motzafi-Haller ( 2011 ), while also enhancing confirmation validity. There were several case studies that would have benefited from improved range and use of data sources, and descriptions of researcher–case interactions (Ajodhia-Andrews & Berman, 2009 ; Bronken et al., 2012 ; Fincham, Scourfield, & Langer, 2008 ; Fourie & Theron, 2012 ; Hooghe et al., 2012 ; Snyder-Young, 2011 ; Yeh, 2013 ).

Study design inconsistent with methodology

Good, rigorous case studies require a strong methodological justification (Meyer, 2001 ) and a logical and coherent argument that defines paradigm, methodological position, and selection of study methods (Denzin & Lincoln, 2011b ). Methodological justification was insufficient in several of the studies reviewed (Barone, 2010 ; Bronken et al., 2012 ; Hooghe et al., 2012 ; Mawn et al., 2010 ; Roscigno et al., 2012 ; Yeh, 2013 ). This was judged by the absence, or inadequate or inconsistent reference to case study methodology in-text.

In six studies, the methodological justification provided did not relate to case study. There were common issues identified. Secondary sources were used as primary methodological references indicating that study design might not have been theoretically sound (Colón-Emeric et al., 2010 ; Coltart & Henwood, 2012 ; Roscigno et al., 2012 ; Snyder-Young, 2011 ). Authors and sources cited in methodological descriptions were inconsistent with the actual study design and practices used (Fourie & Theron, 2012 ; Hooghe et al., 2012 ; Jorrín-Abellán et al., 2008 ; Mawn et al., 2010 ; Rytterström et al., 2013 ; Wimpenny & Savin-Baden, 2012 ). This occurred when researchers cited Stake or Yin, or both (Mawn et al., 2010 ; Rytterström et al., 2013 ), although did not follow their paradigmatic or methodological approach. In 26 studies there were no citations for a case study methodological approach.

The findings of this study have highlighted a number of issues for researchers. A considerable number of case studies reviewed were missing key elements that define qualitative case study methodology and the tradition cited. A significant number of studies did not provide a clear methodological description or justification relevant to case study. Case studies in health and social sciences did not provide sufficient information for the reader to understand case selection, and why this case was chosen above others. The context of the cases were not described in adequate detail to understand all relevant elements of the case context, which indicated that cases may have not been contextually bounded. There were inconsistencies between reported methodology, study design, and paradigmatic approach in case studies reviewed, which made it difficult to understand the study methodology and theoretical foundations. These issues have implications for methodological integrity and honesty when reporting study design, which are values of the qualitative research tradition and are ethical requirements (Wager & Kleinert, 2010a ). Poorly described methodological descriptions may lead the reader to misinterpret or discredit study findings, which limits the impact of the study, and, as a collective, hinders advancements in the broader qualitative research field.

The issues highlighted in our review build on current debates in the case study literature, and queries about the value of this methodology. Case study research can be situated within different paradigms or designed with an array of methods. In order to maintain the creativity and flexibility that is valued in this methodology, clearer descriptions of paradigm and theoretical position and methods should be provided so that study findings are not undervalued or discredited. Case study research is an interdisciplinary practice, which means that clear methodological descriptions might be more important for this approach than other methodologies that are predominantly driven by fewer disciplines (Creswell, 2013b ).

Authors frequently omit elements of methodologies and include others to strengthen study design, and we do not propose a rigid or purist ideology in this paper. On the contrary, we encourage new ideas about using case study, together with adequate reporting, which will advance the value and practice of case study. The implications of unclear methodological descriptions in the studies reviewed were that study design appeared to be inconsistent with reported methodology, and key elements required for making judgements of rigour were missing. It was not clear whether the deviations from methodological tradition were made by researchers to strengthen the study design, or because of misinterpretations. Morse ( 2011 ) recommended that innovations and deviations from practice are best made by experienced researchers, and that a novice might be unaware of the issues involved with making these changes. To perpetuate the tradition of case study research, applications in the published literature should have consistencies with traditional methodological constructions, and deviations should be described with a rationale that is inherent in study conduct and findings. Providing methodological descriptions that demonstrate a strong theoretical foundation and coherent study design will add credibility to the study, while ensuring the intrinsic meaning of case study is maintained.

The value of this review is that it contributes to discussion of whether case study is a methodology or method. We propose possible reasons why researchers might make this misinterpretation. Researchers may interchange the terms methods and methodology, and conduct research without adequate attention to epistemology and historical tradition (Carter & Little, 2007 ; Sandelowski, 2010 ). If the rich meaning that naming a qualitative methodology brings to the study is not recognized, a case study might appear to be inconsistent with the traditional approaches described by principal authors (Creswell, 2013a ; Merriam, 2009 ; Stake, 1995 ; Yin, 2009 ). If case studies are not methodologically and theoretically situated, then they might appear to be a case report.

Case reports are promoted by university and medical journals as a method of reporting on medical or scientific cases; guidelines for case reports are publicly available on websites ( http://www.hopkinsmedicine.org/institutional_review_board/guidelines_policies/guidelines/case_report.html ). The various case report guidelines provide a general criteria for case reports, which describes that this form of report does not meet the criteria of research, is used for retrospective analysis of up to three clinical cases, and is primarily illustrative and for educational purposes. Case reports can be published in academic journals, but do not require approval from a human research ethics committee. Traditionally, case reports describe a single case, to explain how and what occurred in a selected setting, for example, to illustrate a new phenomenon that has emerged from a larger study. A case report is not necessarily particular or the study of a case in its entirety, and the larger study would usually be guided by a different research methodology.

This description of a case report is similar to what was provided in some studies reviewed. This form of report lacks methodological grounding and qualities of research rigour. The case report has publication value in demonstrating an example and for dissemination of knowledge (Flanagan, 1999 ). However, case reports have different meaning and purpose to case study, which needs to be distinguished. Findings of our review suggest that the medical understanding of a case report has been confused with qualitative case study approaches.

In this review, a number of case studies did not have methodological descriptions that included key characteristics of case study listed in the adapted criteria, and several issues have been discussed. There have been calls for improvements in publication quality of qualitative research (Morse, 2011 ), and for improvements in peer review of submitted manuscripts (Carter & Little, 2007 ; Jasper, Vaismoradi, Bondas, & Turunen, 2013 ). The challenging nature of editor and reviewers responsibilities are acknowledged in the literature (Hames, 2013 ; Wager & Kleinert, 2010b ); however, review of case study methodology should be prioritized because of disputes on methodological value.

Authors using case study approaches are recommended to describe their theoretical framework and methods clearly, and to seek and follow specialist methodological advice when needed (Wager & Kleinert, 2010a ). Adequate page space for case study description would contribute to better publications (Gillard et al., 2011 ). Capitalizing on the ability to publish complementary resources should be considered.

Limitations of the review

There is a level of subjectivity involved in this type of review and this should be considered when interpreting study findings. Qualitative methods journals were selected because the aims and scope of these journals are to publish studies that contribute to methodological discussion and development of qualitative research. Generalist health and social science journals were excluded that might have contained good quality case studies. Journals in business or education were also excluded, although a review of case studies in international business journals has been published elsewhere (Piekkari et al., 2009 ).

The criteria used to assess the quality of the case studies were a set of qualitative indicators. A numerical or ranking system might have resulted in different results. Stake's ( 1995 ) criteria have been referenced elsewhere, and was deemed the best available (Creswell, 2013b ; Crowe et al., 2011 ). Not all qualitative studies are reported in a consistent way and some authors choose to report findings in a narrative form in comparison to a typical biomedical report style (Sandelowski & Barroso, 2002 ), if misinterpretations were made this may have affected the review.

Case study research is an increasingly popular approach among qualitative researchers, which provides methodological flexibility through the incorporation of different paradigmatic positions, study designs, and methods. However, whereas flexibility can be an advantage, a myriad of different interpretations has resulted in critics questioning the use of case study as a methodology. Using an adaptation of established criteria, we aimed to identify and assess the methodological descriptions of case studies in high impact, qualitative methods journals. Few articles were identified that applied qualitative case study approaches as described by experts in case study design. There were inconsistencies in methodology and study design, which indicated that researchers were confused whether case study was a methodology or a method. Commonly, there appeared to be confusion between case studies and case reports. Without clear understanding and application of the principles and key elements of case study methodology, there is a risk that the flexibility of the approach will result in haphazard reporting, and will limit its global application as a valuable, theoretically supported methodology that can be rigorously applied across disciplines and fields.

Conflict of interest and funding

The authors have not received any funding or benefits from industry or elsewhere to conduct this study.

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• Open access
• Published: 04 May 2024

Impacts of heat exposure in utero on long-term health and social outcomes: a systematic review

• Nicholas Brink 1 ,
• Darshnika P. Lakhoo 1 ,
• Ijeoma Solarin 1 ,
• Gloria Maimela 1 ,
• Peter von Dadelszen 2 ,
• Shane Norris 3 ,
• Matthew F. Chersich 1 &

Climate and Heat-Health Study Group

BMC Pregnancy and Childbirth volume  24 , Article number:  344 ( 2024 ) Cite this article

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Climate change, particularly global warming, is amongst the greatest threats to human health. While short-term effects of heat exposure in pregnancy, such as preterm birth, are well documented, long-term effects have received less attention. This review aims to systematically assess evidence on the long-term impacts on the foetus of heat exposure in utero.

A search was conducted in August 2019 and updated in April 2023 in MEDLINE(PubMed). We included studies on the relationship of environmental heat exposure during pregnancy and any long-term outcomes. Risk of bias was assessed using tools developed by the Joanna-Briggs Institute, and the evidence was appraised using the GRADE approach. Synthesis without Meta-Analysis (SWiM) guidelines were used.

Eighteen thousand six hundred twenty one records were screened, with 29 studies included across six outcome groups. Studies were mostly conducted in high-income countries ( n  = 16/25), in cooler climates. All studies were observational, with 17 cohort, 5 case-control and 8 cross-sectional studies. The timeline of the data is from 1913 to 2019, and individuals ranged in age from neonates to adults, and the elderly. Increasing heat exposure during pregnancy was associated with decreased earnings and lower educational attainment ( n  = 4/6), as well as worsened cardiovascular ( n  = 3/6), respiratory ( n  = 3/3), psychiatric ( n  = 7/12) and anthropometric ( n  = 2/2) outcomes, possibly culminating in increased overall mortality ( n  = 2/3). The effect on female infants was greater than on males in 8 of 9 studies differentiating by sex. The quality of evidence was low in respiratory and longevity outcome groups to very low in all others.

Conclusions

Increasing heat exposure was associated with a multitude of detrimental outcomes across diverse body systems. The biological pathways involved are yet to be elucidated, but could include epigenetic and developmental perturbations, through interactions with the placenta and inflammation. This highlights the need for further research into the long-term effects of heat exposure, biological pathways, and possible adaptation strategies in studies, particularly in neglected regions. Heat exposure in-utero has the potential to compound existing health and social inequalities. Poor study design of the included studies constrains the conclusions of this review, with heterogenous exposure measures and outcomes rendering comparisons across contexts/studies difficult.

Trial Registration

PROSPERO CRD 42019140136.

Peer Review reports

Introduction

Climate change is one of the most significant threats to human health [ 1 ], characterized by an increase in global temperatures amongst other environmental changes. Global temperatures have increased by approximately 1·2 °C, and are projected to increase beyond a critical threshold of 1·5 °C in the next 5–10 years [ 2 ]. Increasingly, heat exposure is being linked with a multitude of short- and long-term health effects in vulnerable populations, including children [ 3 ], the elderly, and pregnant women [ 4 ]. The effect on pregnant women extends to the health of the foetus, with significant detrimental effects associated with heat exposure including preterm birth, stillbirth, and decreased birth weight [ 5 ]. Impacts of heat exposure are increasingly important in populations in resource-constrained settings, where heat adaptation measures such as active (air-conditioning) and passive cooling (water, green and blue spaces) are limited, and often inaccessible [ 6 ]. These populations are often found in some of the hottest climates and in areas whose contribution to global warming is negligible, thus compounding inequities [ 7 ]. In addition, research in this field is biased towards Europe, North America and Asia and is profoundly underrepresented in Africa and South America [ 8 ]. Understanding the scope and distribution of research conducted is key to guiding future research, including biological studies to explore possible mechanisms, and interventional studies to alleviate any observed negative effects. Multiple previous systematic reviews have explored the short-term impacts of heat on the foetus [ 3 , 5 , 9 ] but only one has explored the long-term impacts of heat exposure on mental health [ 10 ]. The in-utero environment has long been considered important in the long-term health and wellbeing of individuals [ 11 , 12 ], although it has been challenging to delineate specific causal pathways. This study aims to systematically review the literature on the long-term effects of heat exposure in-utero on the foetus, and explore possible casual pathways.

Materials and methods

This review forms part of a larger systematic mapping survey of the effect of heat exposure, and adaptation interventions on health (PROSPERO CRD 42019140136) [ 13 ]. The initial literature search was conducted in September 2018, where the authors searched MEDLINE (PubMed), Science Citation Index Expanded, Social Sciences Citation Index, and Arts and Humanities Citation Index using a validated search strategy (Supplementary Text 1 ). This search was updated in April 2023 through a MEDLINE search, as all previous articles were located in this database. Screening of titles and abstracts was done independently in duplicate, with any differences reconciled by MFC, with subsequent updates conducted by NB and DL. The authors only included studies on humans, published in Chinese, English, German, or Italian. Studies on heat exposure from artificial and endogenous sources were excluded, and only exogenous, weather-related heat exposure during pregnancy was included. All study designs were eligible except modelling studies and systematic reviews. No date restrictions were applied. EPPI-Reviewer software [ 14 ] provided a platform for screening, reviewing of full text articles, and for data extraction. No additional information was requested or provided by the authors. Long-term effects were defined as any outcomes that were not apparent at birth.

Articles meeting the eligibility criteria were extracted in duplicate after the initial search and then by a single reviewer in the subsequent update (NB/DL). Data were extracted to include characteristics outlined in Supplementary file 1 .

This systematic review was conducted according to the Systematic Review without Meta-Analysis (SWiM) guidelines, broadly based on PRISMA [ 15 ], as the outcomes, statistical techniques, and heat exposure measurements were heterogenous, rendering a meta-analysis untenable. Outcomes were grouped clinically, reviewed for the magnitude and direction of effect, and their statistical significance, and included negative or null findings when reported on. A text-based summary of these findings was made. ‘Vote-counting’ was utilized to summarise direction of effect findings. Analysis was conducted on the geographical areas, climate zones [ 16 ], mean annual temperature and socioeconomic classification of the country where the studies were conducted. Furthermore, an attempt was made to identify at-risk population sub-groups.

The principal investigator assessed each study for a risk of bias using the tools developed by the Joanna-Briggs Institute (JBI) [ 17 ] (Supplementary file 1 ). Each study was classified as high or low risk of bias. Studies that did not score ‘yes’ on two or more applicable parameters were classified as high risk of bias [ 5 ]. Due to the limited research in this field, no studies were excluded based on risk of bias. The certainty of the evidence was assessed using the GRADE approach, with the body of evidence assessed on a scale of certainty: very low, low, moderate and high  [ 18 ]. Due to the heterogeneity of outcomes, and the reporting thereof, assessment of publication bias was not possible.

The funder of the study had no role in study design, data collection, analysis, interpretation, or writing of the report.

The updated search identified 18 621 non-duplicate records, and after screening 229 full-text articles were reviewed for inclusion, with a total of 29 studies included in the final analysis (Fig.  1 : flow chart). The included studies were conducted in 25 countries across six continents, including six Low-Income Countries (LIC), two Lower-Middle Income Countries (LMIC), one Upper-Middle Income Country (UMIC) and 16 High Income Countries (HIC) [ 19 ]. They included 25 Köppen-Geiger climate zones [ 16 ], and mean annual temperatures ranging from 2.1 °C in Norway to 30.0 °C in Burkina Faso [ 20 ] (Figs.  2 and 3 ). All studies were observational, with 17 cohort, five case-control and eight cross-sectional studies. The timeline of the data is from 1913 to 2019, and individuals included ranged in age from neonates to adults, and the elderly. The studies were grouped by outcomes as follows: behavioural, educational and socioeconomic ( n  = 6), cardiovascular disease ( n  = 6), respiratory disease ( n  = 3), growth and anthropometry ( n  = 2), mental health ( n  = 12) and longevity and mortality ( n  = 3). The measures of heat exposure were variable, with minimum, mean, maximum, and apparent temperature being utilized, as well as temperature variability, heat wave days and discreet shocks (number of times exposure exceeded a specific threshold). The majority of studies measured heat using mean temperature ( n  = 27/29). In addition, the statistical comparison was diverse, with some studies making a continuous linear comparison by degree Celsius, while others compared heat exposure by quartiles, amongst other categorical comparisons. Furthermore, heat exposure by any definition was not reported over the same timeframes, with some studies including variable periods before birth, during pregnancy and at birth in their analysis. Levels of temporal resolution of heat exposure were also diverse, ranging from monthly effects to effects observed over the entire gestational period, or year of birth. In addition, differing use of heat adaptation mechanisms was not uniformly described and adjusted for. Various confounders were adjusted for, and although not uniform, these were generally inadequate. The effect on female infants was greater than on male infants in eight of nine studies differentiating by sex, with increased effects on marginalised groups (African-Americans) in one further study. Overall, the quality of the evidence, as assessed by the GRADE approach, was low in respiratory and longevity outcome groups to very low in all other groups, primarily as a result of their observational nature and high risk of bias, due to insufficient consideration of confounders, and inadequate measures of heat exposure.

PRISMA flow diagram

Map showing countries where studies were conducted relative to mean annual temperature [ 21 ]

Map showing countries where studies were conducted relative to climate zones [ 16 ]

A total of six studies reported on behaviour, educational and socioeconomic outcomes, which were detrimentally affected by increases in heat exposure (Fig.  4 ; Table  1 ), although the quality of the evidence was very low . End-points were not uniform, but included earnings, completion of secondary school or higher education, number of years of schooling, and gamified cooperation-rates in a public-goods game (where test scores represent achieving maximal public benefit in hypothetical situations).

Two large studies reported a detrimental effect of heat exposure on adult income, with the greatest effect noted in first trimester exposure. These studies noted a reduction in earnings of up to 1·2% per 1 °C increase in temperature, with greater effects in females [ 22 ], and a decrease of $55.735 (standard error(SE): 15·425, P  < 0·01) annual earnings at 29–31 years old, per day exposure > 32 °C [ 26 ]. Two studies reported worse educational outcomes, with the greatest effect noted in the second trimester [ 23 ]. Rates of completing secondary education were found to be reduced by 0·2% per 1 °C increase in temperature ( P  = 0·05) [ 22 ], illiteracy was increased by 0·18% (SE=(0·0009); P  < 0·05) and mean years of schooling was lowered by 0.02 (SE=(0·009) P  = 0·07) [ 23 ]. Two studies reported a beneficial effect of heat exposure on educational outcomes, although both studies suffered from significant methodological flaws, and effects were < 0·01% when effect estimates were noted [ 24 , 27 ]. One small study reported lower cooperation rates by 20% ( P  < 0·01) in a public-goods game, with lower predicted public wellbeing [ 25 ].

The studies generally exhibited a dose-response effect with evidence for a critical threshold of effect of 28 °C in one study [ 22 ]. All studies were at a high risk of bias.

Figure showing vote counting across all outcome groups. No Effect = No direction of effect noted in study

Six studies reported on cardiovascular pathology and risk factors thereof, which were detrimentally affected by increased exposure to heat (Fig.  4 ; Table  2 ), although measures and surrogates of this outcome were heterogenous. The quality of the evidence was very low, and the sample sizes were small. Outcomes included blood pressure, a composite cardiovascular disease indicator, and specific cardiovascular disease risk factors such as diabetes mellitus (type I), insulin resistance, waste circumference, and triglyceride levels.

Three studies found a detrimental effect of heat exposure on hypertension rates, and increased blood pressure [ 31 ], with a maximum of 1·6 mm Hg increase noted per interquartile range (IQR) increase (95% Confidence interval (CI) = 0·2, 2·9, P  = 0·024) in children [ 30 ], with increased effects on women in the largest study ( N  = 11,237) [ 32 ]. Another study found increasing heat exposure at conception was detrimentally associated with an increase in coronary heart disease ( P  = 0·08) [ 32 ], although one of the smaller studies ( N  = 4286) found a beneficial effect of heat exposure at birth on diverse cardiovascular outcomes, including coronary heart disease ( P  = 0·03 for trend), triglyceride levels ( P  = 0·06 for trend) and insulin resistance ( P  = 0·04 for trend) [ 27 ]. One study found lower odds of type I diabetes mellitus with increasing heat exposure, with odds ratio (OR) = 0·73 (95%CI = 0·48, 1·09, P -value not stated) [ 28 ]. Another study did not detect statistically significant relationships between heat exposure and hypertension or a composite cardiovascular disease indicator, but did not provide effect estimates [ 29 ]. Five studies were at a high risk of bias [ 27 , 29 , 30 , 31 , 32 ], with only one case-control study at a low risk of bias [ 28 ].

Respiratory pathology was reported by three studies, assessing different outcomes. Outcomes were detrimentally associated with increasing heat (Fig.  4 ; Table  3 ), however the quality of the evidence was low . The outcomes were primarily measured in infants and children, with no studies on adult outcomes. The largest study ( N  = 1681) found that increasing heat exposure increased the odds of having childhood asthma [ 33 ], and another small study ( N  = 343) noted worsened lung function with increasing heat exposure [ 34 ].

An additional study noted increased odds of childhood pneumonia with increasing diurnal temperature variation (DTV) in pregnancy, with a maximum OR = 1·85 (95%CI = 1·24, 2·76) in the third trimester [ 35 ].

Exposure in the third trimester had the greatest effect across all three studies [ 33 , 34 , 35 ]. Females showed an increased susceptibility to heat exposure’s effects on lung function, but males were more susceptible to heat’s effect on childhood pneumonia. There was a critical threshold noted in the asthma study of 24·6 °C, with a dose-response effect. The asthma study was assessed as low risk of bias, however the other studies were at high risk.

Growth and anthropometry was reported on by two studies, with differing outcomes, although in both, heat exposure was associated with detrimental, although heterogenous, outcomes (Fig.  4 ; Table  4 ). The overall quality of the evidence was very low . One study found a positive association with heat exposure and increased body mass index (BMI), r  = 0·22 ( P  < 0·05) in the third trimester with greater effects noted in females and in African-Americans [ 36 ]. Another large study ( N  = 23 026) found increased odds of stunting (OR = 1·28, 95%CI = not stated, p  < 0·001) with a negative correlation with height noted ( r =-0·083 P  < 0·01) [ 37 ]. Effects were greatest in the first and third trimester. Both studies were at a high risk of bias.

Mental health was reported on by 12 studies. Increasing heat exposure generally had a detrimental association with mental health outcomes (Fig.  4 ; Table  5 ), although these were heterogenous. The overall quality of the evidence was very low . Five studies reported on schizophrenia rates, with only one study showing a strongly positive association of heat exposure at conception with schizophrenia rates ( r  = 0·50, p  < 0·025) [ 38 ]. Another study noted the same effect with increasing heat in the summer before birth, however this was not statistically significant [ 39 ]. The third study reported no association of this outcome [ 40 ], with another small study ( N  = 2985) showing a negative correlation with temperatures at birth, without reporting on heat exposure during other periods of gestation [ 41 ]. The fifth study failed to report direction of effect, but noted non-significant findings [ 42 ]. Six studies reported on eating disorders, with all six showing a detrimental effect with increasing heat exposure. Of the three studies on clinical anorexia nervosa, one reported increasing rates of anorexia nervosa compared to other eating disorders (χ²= 4·48, P  = 0·017) [ 43 ], another reported increasing rates of a restrictive-subtype (χ²= 3·18, P  = 0·04) as well as reporting worse assessments of restrictive behaviours [ 44 ], which was supported by a third study in a different setting [ 45 ]. Three studies examined non-clinical settings, with some inconsistent effects. The first study showed a weak positive association with heat exposure, and drive for thinness (Spearman’s ⍴ = 0·46, P  < 0·05) and bulimia scores (Spearman’s ⍴ = 0·25, P  < 0·05) [ 46 ], which was supported by a replication study [ 47 ], and one other study [ 48 ]. The most significant and consistent effects noted in the third trimester, at birth, and in females [ 47 , 48 ]. One study reported a beneficial effect of increased temperatures in the first trimester on rates of depression, however no other directions of effect were noted for other periods of exposure [ 49 ]. These studies were at a high risk of bias.

Increasing heat exposure had a detrimental effect on longevity and mortality across various outcomes (Fig.  4 ; Table  6 ), although despite large sample sizes, the quality of the evidence was low . One study found a negative correlation of heat exposure with longevity ( r =-0·667, P  < 0·001), with a greater effect on females [ 50 ]. A second study showed a detrimental effect on telomere length, as a predicter of longevity, with the greatest effect towards the end of gestation (3·29% shorter TL, 95%CI = − 4·67, − 1·88, per 1 C increase above 95th centile) [ 51 ]. Conversely, a third study noted no correlation with mortality [ 24 ]. All but the study on telomere length [ 51 ] were at a high risk of bias.

This study establishes significant patterns of effects amongst the outcomes reviewed, with increasing heat exposure being associated with an overall detrimental effect on multiple, diverse, long-term outcomes. These effects are likely to increase with rising temperatures, however modelling this is beyond the scope of this review.

The most notable detrimental outcomes are related to neurodevelopmental pathways, with behavioural, educational, socioeconomic and mental health outcomes consistently associated with increasing heat exposure, in addition to having the greatest body of literature to support this. Importantly, other systems such as the respiratory and cardiovascular systems also suggest harmful effects of heat exposure, culminating in detrimental associations with longevity and mortality. Some studies illustrated a possible beneficial effect in some disease-processes, such as coronary heart disease and depression showing the potential for shifting disease profiles with rising temperatures.

The detrimental effects of heat exposure became more significant with increasing temperatures, with many studies describing increasing effects beyond critical thresholds which, although varied across studies, suggest that there is a limit of heat adaption strategies, both biological and behavioural [ 52 , 53 ].

In addition, the effect of increasing heat exposure was associated with worse outcomes in already marginalised communities, such as women [ 22 , 32 , 34 , 36 , 44 , 47 , 48 , 50 ] and certain ethnic groups (African-Americans) [ 46 ]. The reasons for sub-population vulnerabilities are unclear and likely complex. In the case of female foetuses being more susceptible to changes in the in-utero environment, it is possible that there is a ‘survivorship bias’. This would occur if women with harmful exposure lose male infants during pregnancy at a higher rate, and thus the surviving female infants appear more at risk. However, despite an increased risk of early pregnancy loss, there are no studies that have assessed this differential vulnerability. This still has the effect of potentially increasing the burden of disease on an already marginalised group.

In the case of certain population groups being more at risk, it is likely that both physiological differences in vulnerability as well as socio-economic effect-modifiers exist to explain these differences, however, the included literature lacks sufficient evidence to assess this. The vulnerabilities of different populations to the long-term effects of heat exposure in-utero likely contributes to the unequal impacts of climate change that have already been established [ 54 ], and will be an important contributor to inequality with future increases in temperature. Further research in this area is critical to inform targeted redistributive interventions.

Although the associations may be clear, establishing causality is fraught with difficulty, with no consensus on an infallible approach [ 55 , 56 , 57 ]. However, it is prudent to highlight supporting evidence in this review.

The hypothesis that the in-utero environment had significant long-term impacts on the foetus was first suggested by Barker, in the context of maternal nutrition and cardiovascular disease [ 11 ]. Further studies supported this hypothesis, and expanded on the effects the in-utero environment has on the foetus and its long-term wellbeing [ 58 ]. Long-term heat exposure may also be associated with changes in nutritional availability [ 11 ], and is likely one of many complex but important environmental exposures in-utero.

Maternal comorbidities, associated with increasing heat exposure such as hypertensive disorders of pregnancy and gestational diabetes mellitus, are known to negatively affect the foetus in the long-term [ 59 , 60 ]. These comorbidities may be part of the long-term pathogenicity of heat exposure, through short-term exposure-outcome pathways. Placental dysfunction is central to the pathology of pre-eclampsia, and is a significant cause for foetal pathology [ 61 , 62 ]. The placenta is not auto-regulated and is therefore acutely affected by changes to blood volume, heart rate and blood pressure, culminating in cardiac output as it is delivered to the placenta as an end-organ with resultant negative effects on the foetus [ 63 ]. Heat-acclimatisation mechanisms are hypothesized to affect this delicate balance [ 52 , 64 ], with observational studies supporting this [ 64 ]. It has been suggested that heat exposure’s increase in inflammation is a possible causative mechanism for pre-term birth [ 5 , 52 ], but inflammation has numerous additional effects on the immune system and could prove an insult to the mother and developing foetus [ 62 , 65 ]. These effects may only manifest in the long-term.

Heat was one of the earliest described teratogens [ 66 ], with significant effects on neurodevelopment noted in animal models in keeping with the observed associations of this review [ 67 ]. Biological organisms are extremely dependent on heat as a trigger for various processes. Plants and animals undergo significant change in response to the seasons, which are often guided by fluctuations in temperature. These changes are often mediated by epigenetic mechanisms, allowing the modification and modulation of gene expression [ 68 , 69 ].

Thus, from an evolutionary perspective, DNA, is sensitive to changes in temperature. The mechanism of this sensitivity has been shown to be primarily epigenetic in nature [ 69 ]. Increasing heat results in modifications to histone deacetylation and DNA methylation [ 69 ]. This is required to provide fast-acting adaptions to acute stressors, but can have long-term effects too [ 70 ]. Thus, it is likely that humans are sensitive to changes in temperature, which can alter epigenetic modifications, and thus our exposome. This sensitivity, may have provided a survival benefit in times of increasing heat, or it may simply be a vestigial function which provides no survival benefit, and may in fact have detrimental effects [ 71 ]. Epigenetic changes have been shown to have significant effects on metabolic diseases and risk profiles, and an in-depth review is provided by Wu et al. [ 72 ]. The exact processes and genes involved would be an area requiring further research, where similar research exists on the effects of nutrition on exact epigenetic pathways [ 73 ]. An important pattern requiring further research involves the effect heat may have on neurodevelopment [ 67 , 74 ]. The above pathways provide additional mechanisms for the long-term lag between exposure-outcome pathways. In addition, acute heat exposure at the time of birth has been associated with various possibly pathogenic mechanisms such as preterm birth [ 5 ], low APGAR scores [ 75 ] and foetal distress [ 76 ], as well as a possible effect on the maternal microbiome and the seeding thereof to the neonate [ 10 , 64 , 77 , 78 ]. These effects, can all provide plausible causes for the long-term outcomes observed through short-term insults. The interplay of these, and additional factors is highlighted in Fig. 5 [ 79 ]. Importantly, the periods of vulnerability are likely different for these various pathways, but specific outcomes may have multiple periods of vulnerability through different pathways.

Causal pathways

The outcomes associated with increasing heat exposure highlight the health, social, and economic cost of global warming, establishing current estimates and future predictions for this are beyond the scope of this research but would provide a valuable area for future research. This would entail estimating disease-burden due to climate change through attribution studies. Traditional health impact studies conflate adverse outcomes from natural variations in climate (‘noise’) with adverse outcomes from anthropogenic climate change. However, not every climate-related adverse outcome is the result of anthropogenic climate change, and these effects are likely different in vulnerable populations. This highlights the benefit of studying and implementing effective heat adaptation strategies in areas where the greatest effect is likely to be observed, and where the greatest impacts in lessening the economic and human impact of global warming are possible [ 80 , 81 ].

Limitations

The difficulty in assessing the data is compounded by the heterogenous measures of heat exposure. No studies used widely accepted heat exposure indices that consider important environmental modifying factors like humidity and windspeed [ 82 , 83 ]. In addition, effect modifiers, heat acclimatisation and adaptation strategies were seldom considered [ 84 , 85 , 86 ]. It may be prudent for future studies to consider the measure of ionizing radiation exposure as an analogous environmental exposure, where different measures exist for the intensity, total quantity (a function of duration of exposure) and biologically-adjusted quantity absorbed [ 87 ]. Differing time-periods of exposure made it difficult to evaluate specific periods of sensitivity, which are likely different for various outcomes, depending on critical periods of development.

Despite consistency across different contexts in this review, the analysis of the distribution of the included studies highlights the unequal weight of studies towards relatively cooler climates, in regions with higher socioeconomic levels and likely greater heat adaptation uptake, and must therefore be interpreted in this context. It is possible that myriad factors that differ geographically, including physiological and socio-economic differences, will influence the effects of heat, and thus there is likely no underlying universal truth to associations and effect estimates.

Quantifying, describing and comparing the effect size across studies was rendered more difficult due to heterogenous statistical analyses.

Although some studies adjusted for possible confounding variables, not all reported on this, with the effects of seasonal, foetal, and maternal biological factors that may not lie on the causal pathway seldom considered [ 3 , 5 , 9 , 88 , 89 , 90 , 91 , 92 ].

Data extraction and assessment of risk of bias was not uniformly undertaken in duplicate due to resource constraints, which may predispose to extraction errors or bias. The high risk of bias of included studies, limits the utility of the overall assessment of effects and suggestions for further action. In addition, publication bias is likely skewing the results towards statistically significant detrimental results, with studies with smaller sample sizes not necessarily showing wider distribution of findings as would be expected.

Climate change, and in particular, global warming, is a significant emerging global public health threat, with far reaching, and disproportionate effects on the most vulnerable populations. The effects of increasing heat exposure in utero are associated with, and possibly causal in, wide-ranging long-term impacts on socioeconomic and health outcomes with a significant cost associated with increasing global temperatures. This association is as a result of a complex interplay of factors, including through direct and indirect effects on the mother and foetus. Further research is urgently required to elicit biological pathways, and targets for intervention as well as predicting future disease-burden and economic impacts through attribution studies.

Availability of data and materials

This study was a review of publicly available information data, with references to data sources made in the reference list.

Abbreviations

Apparent Temperature

Body Mass Index

Blood Pressure

Coronary Heart Disease

Confidence Interval

Diastolic Blood Pressure

Eating Disorder Inventory

Functional Residual Capacity

Interquartile Range

Non-Significant

Respiratory Rate

Systolic Blood Pressure

Standard Error

Telomere Length

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Brink, N., Lakhoo, D.P., Solarin, I. et al. Impacts of heat exposure in utero on long-term health and social outcomes: a systematic review. BMC Pregnancy Childbirth 24 , 344 (2024). https://doi.org/10.1186/s12884-024-06512-0

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Original research article, virtual surgical planning/3d printing assisted fibula osteoseptocutaneous flap combined with anterolateral thigh flaps for extensive composite oromandibular defects reconstruction: a retrospective study of case series.

• 1 Department of Oral and Maxillofacial Surgery, The Affiliated Hospital of Qingdao University, Qingdao, China
• 2 School of Stomatology, Qingdao University, Qingdao, China
• 3 Dental Digital Medicine and 3D Printing Engineering Laboratory of Qingdao, Qingdao, China
• 4 Shandong Provincial Key Laboratory of Digital Medicine and Computer-Assisted Surgery, Qingdao, China

Oromandibular tumors or osteoradionecrosis often lead to extensive composite defects encompassing intraoral, bone and extraoral tissues. A single flap cannot simultaneously offer sufficient bone and soft tissue. The combination of free flaps could be a prospective approach to overcome the challenge. The study aims to assess the efficacy of virtual surgical planning (VSP) and 3D printing assisted fibula osteoseptocutaneous flap (FOSCF) combined with anterolateral thigh flaps (ALT) in reconstructing extensive composite defects in the oromandibular region. A retrospective analysis was conducted on 8 patients who underwent reconstruction using FOSCFs combined with ALTs. Post-surgical excision of the lesions, we obtained mean values for the defects of intraoral soft tissue, bone, extraoral soft tissue, namely, being 42.7 cm 2 , 96 mm, and 68.9 cm 2 . The mean surgical procedures took 712.5 min. A total of 16 flaps were harvested and transplanted for the 8 patients, with all successfully surviving. Postoperatively, complications manifested as localized intraoral infections in 2 cases, intermuscular vein thrombosis in another 2 cases, and pulmonary infections in 2 patients. Two patients unfortunately experienced tumor recurrence, at 12 and 3 months post-operation respectively. For the surviving 6 patients, the average follow-up period was 12.2 months. Regarding patient satisfaction, one expressed dissatisfaction with the contour of the mandible, and two exhibited moderate trismus. Objective assessments identified 1 case of oral incontinence and 2 cases where external flap contractures were observed. All 8 patients experienced restoration of masticatory function and were able to consume a soft diet within a month post-surgery. VSP/3D printing assisted FOSCFs combined with ALTs can be performed safely to reconstruct the extensive composite tissue defects in our study, with desirable esthetic and functional results, and it is a reliable option in selecting patients with defects involving multiple tissue types. However, the benefits of this method needed more cases to validate.

1 Introduction

Extensive composite oromandibular defects are frequently caused by surgical resection of sizeable primary tumors in the head and neck region, or the result of osteoradionecrosis (ORN) post-radiotherapy. The reconstruction of such complex defects, encompassing multiple structures such as external skin, mandible, and oral mucosa presents a formidable challenge. Free flap reconstruction is the standard of care in these extensive defects, while there may not exist a single free flap capable of simultaneously offering sufficient bone stock and soft tissue. In these instances, the combination of multiple free flaps proves to be an efficacious treatment strategy ( Lee et al., 2010 ; Weitz et al., 2015 ).

Selecting suitable free flap is integral to the reconstructive success and overall outcome. In contrast to iliac or scapular osteocutaneous free flaps, the FOSCF can provide longer bone segments as well as ample skin paddle for intraoral lining ( Taylor et al., 2016 ; Liu et al., 2022 ). The ALT is the most useful workhorse flap employed for microsurgical reconstruction. Depending on requirements, the flap can be harvested as myocutaneous, fasciocutaneous, adipofascial, or in combination with the adjacent tissues or muscles as chimeric flaps. This versatility makes it particularly suited for the reconstruction of extensive extraoral skin defects ( Hsieh et al., 2021 ; Ranganath et al., 2022 ). The advent of VSP and 3D printing marks a significant milestone for the FOSCF. The utilization of these techniques enhances the safety, accuracy, and symmetry of this surgical procedure while considerably reducing the operating time ( Ritschl et al., 2021 ; Al-Sabahi et al., 2022 ; Idris et al., 2022 ).

Despite their advantages, multi-flap approaches for the reconstruction of composite oromandibular defects continue to be challenging and are a subject of ongoing debate. A few reports are available on the functional and aesthetic outcome of double free flap reconstructions in these defects ( Lee et al., 2010 ; Tharakan et al., 2023 ). The objective of this study is to evaluate the effect of the combination of VSP/3D printing-assisted FOSCF with ALT in composite tissue defects reconstruction which could not be solved by one single flap.

2 Patients and methods

This study received approval from the Ethics Committee at the Affiliated Hospital of Qingdao University, Qingdao (ethics number, QYFYWZLL 27958). A retrospective review was conducted of 8 patients who underwent extensive composite oromandibular defects repair using the combination of VSP/3D printing-assisted FOSCF with ALT between July 2019 and December 2022 at our department.

The cohort comprised seven males and one female. All patients had undergone lesion resection, with extensive defects variably involving oral mucosa, mandible, and perioral skin areas. All defects were reconstructed using a FOSCF in combination with ALT. A two-team approach was consistently employed throughout all stages of the operation.

2.1 Preparation of the FOSCF assisted by VSP and 3D printing

All patients underwent routine preoperative three-dimensional CT scan of the mandible and fibula (SOMATOM Force CT, slice thickness 0.625 mm), in addition to lower limb CT angiography (CTA). The acquired data were input into the Mimics 17.0 software (Materialise, Leuven, Belgium) in the DICOM format. The software was used to simulate tumor excision, fibula osteotomy, mandibular reconstruction, and the design of repositioning guides. In the process, the mandibular osteotomy guide and the fibula positioning guide share the same nail track to ensure the accuracy of mandibular reconstruction. For those mandibular defects not traversing the midline, mirror technology was employed to accomplish reconstruction. However, in cases where the defects did cross the midline, a synergistic approach combining mirror and surface reconstruction techniques was adopted. Following the completion of the virtual surgery, the designed guides were materialized using an 3D printer (UltraCraft A2D, HeyGears), and subsequently sterilized with plasma. The reconstruction-team prepared the FOSCF. The skin perforator was located and the skin paddle was incised in accordance with the magnitude of the intraoral soft tissue defect. The fibula osteotomy guide was positioned, leading to the fibula being cut to the length prescribed in the virtual surgery. The distal end of the fibular artery was ligated, preserving the proximal vascular pedicle. The fibula was then contoured using the shaping guide and secured in position with miniplates. Upon completing the FOSCF preparation, the same team proceeded to harvest the ALT.

2.2 Oral lesion excision

The resection-team was tasked with the excision of the tumor at its safe boundary. According to the preoperative virtual surgical design, the mandibular osteotomy guide was positioned, followed by the segmental resection of the mandible. After the complete excision of the tumor, two sets of recipient vessels were prepared. Subsequent to the surgical procedure, patients were admitted to the intensive care unit (ICU), and tracheostomy was not a routine intervention. Patients were typically transferred back to the general ward within a period of 3–5 days postoperatively, contingent upon their stabilized condition. All patients needed nasogastric feeding for 1 week post-surgery. Subsequently, a soft or normal diet was gradually adopted. All patients except No.5 and No.8 underwent postoperative radiation therapy.

Surgical and medical complications were documented. A patients satisfaction questionnaire was administered to make subjective evaluation on chewing, speech, dry mouth and facial appearance, which were divided into three grades: very satisfied, satisfied and dissatisfied. To determine objective evaluation, facial appearance, oral incontinence, speech problems, eating problems, xerostomia, and flap contracture were assessed. Each individual item was scored using a Likert scale (1 = extremely abnormal and 5 = completely normal).

Our study comprised 8 patients including 7 males and 1 female, aged from 45 to 68 years (mean, 60.5 years). Seven of these patients presented with oral malignant tumors, all diagnosed as squamous cell carcinoma, while one patient (No.5) had osteoradionecrosis as a consequence of radiation therapy. A total of 16 flaps were prepared for 8 patients, which consisted 8 FOSCFs and 8 ALTs. Post-excision of the lesions, the dimensions of the intraoral soft tissue defects ranged from 7.5 × 4 cm to 12 × 6.5 cm (mean, 42.7 cm 2 ). The length of the bone defects extended from 76 mm to 125 mm (mean, 96 mm), while the extraoral soft tissue defects varied from 8 × 5 cm to 14 × 9 cm (mean, 68.9 cm 2 ). The anastomosis involved recipient arteries that included the facial artery, superior thyroid artery, and lingual artery. Concurrently, the recipient veins involved were the facial vein, superior thyroid vein, internal jugular vein, and external jugular vein. One case required vascular grafting. The operative duration for these procedures ranged between 600 and 840 min, with an average of approximately 712.5 min ( Table 1 ).

TABLE 1 . Patient data.

Remarkably, all of the flaps survived without any vascular crises or local flap necrosis. Two cases (No.3, No.4) developed local oral infections. Additionally, intermuscular vein thrombosis in the lower limbs was observed 2 patients (No.2, No.5). Pulmonary infection was found in 2 cases (No.2, No.4). Unfortunately, 2 of the 8 patients succumbed due to tumor recurrence at 12 months and 3 months post-surgery respectively. The mean follow-up time of the remaining 6 patients was 12.2 months (range, 7 months–18 months). Patient satisfaction assessments revealed one individual (No.3) was dissatisfied with their post-operative appearance, while two (No.2, No.4) reported moderate trismus. However, the remaining patients all reported satisfaction levels above average. Objective evaluations indicated oral incontinence in 1 case (No.4) and external flap contracture in 2 cases (No.2, No.4). Impressively, all 8 patients regained masticatory function and resumed a soft diet within a month post-operation.

3.1 Case presentation

A 45-year-old male patient diagnosed with a squamous cell carcinoma on his left cheek. The tumor demonstrated regression by radiation therapy (66 Gy) 7 months ago. However, the anterior part was ulcerated and gradually formed a penetrating defect after 1 month. Histopathological examination confirmed squamous cell carcinoma, staged clinically as T4N1M0. With the assistance of VSP and 3D printing technology, the reconstruction utilising both flaps was successfully performed ( Figures 1 , 2 ).

FIGURE 1 . The preoperative virtual surgical design: (A) . Determine the range of the lesion. (B) Simulate the range of bone cutting. (C) Design the bone cutting guide. (D) Design the fibula osteotomy guide. (E) Design the fibula repositioning guide. (F) Restore the mandibular contour.

FIGURE 2 . Operational procedure: (A) . Preoperative photo. (B) Fibula shaping. (C) Fibula positioning. (D) Harvest of the ALT. (E) The fibula osteoseptocutaneous flap was used to repair the oral soft tissue and the mandible, and the ALT was used to repair the extraoral tissues. (F) 6 months post-operation.

4 Discussion

Surgical removal of oral tumors or osteoradionecrosis can result in substantial composite tissue defects, presenting formidable challenges for reconstructive repair. A single flap is often insufficient to adequately address these extensive defects. Consequently, the combination of multiple flaps has emerged as an innovative therapeutic approach ( Lee et al., 2010 ; Weitz et al., 2015 ; Hsieh and Bewley, 2019 ; Silva et al., 2019 ; Moratin et al., 2021 ; Raghuram et al., 2021 ; Santilli et al., 2021 ; Tharakan et al., 2023 ). The ALT can furnish sufficient tissue volume and can be fashioned into a chimeric flap with minimal impact on the donor site, rendering it an optimal choice for repair and reconstruction of large soft tissue defects in the oromandibular region ( Thomas et al., 2020 ). The FOSCF is exceptionally suitable for large bone tissue defects. Its accompanying skin paddle can repair tissues both inside or outside the oral cavity, and its associated muscle can effectively fill the surgical dead space ( Dowthwaite et al., 2013 ). Therefore, for large composite tissue defects in the oromandibular region, we opt for the ALT for the repair of extraoral soft tissue defects and the FOSCF for the repair of bone and intraoral soft tissue defects. Nevertheless, surgical alternatives should be carefully considered. The fibular flap can be substituted with a reconstruction plate, iliac bone muscle flap, or scapular bone muscle flap. Soft tissue flap can be replaced with a vascularized free flap or pedicled flap, such as the forearm flap, rectus abdominis flap, or pectoralis major myocutaneous flap. However, the radial forearm flap offers limited soft tissue volume, it is difficult to fill the dead cavity effectively. Its application is further limited by the severe scarring left on the forearm, tendon exposure, and forearm mobility disorders ( Ranganath et al., 2022 ). The rectus abdominis myocutaneous flap can deliver a satisfactory volume of soft tissue, yet it may trigger complications such as reduced abdominal wall strength and incisional hernia. While the pectoralis major flap supplies generous soft tissue, it’s typically considered a backup option. The free iliac flap has insufficient bone length to adequately repair the defects. Besides, the free scapular flap cannot effectively mimic the shape of the mandibula, and has limitations in deficient bone length ( Liu et al., 2022 ). Moreover, reconstruction plates are prone to complications like screw loosening, plate fracture, plate exposure and stress shielding.

A unique aspect of our study is the incorporation of VSP and 3D printing. VSP allows for tailoring surgical approaches, ensuring precise lesion delineation, osteotomy localization, and fibula harvest estimation. Preoperative mandibular modeling not only reduces surgical time but also ensures superior functional and aesthetic outcomes. 3D-printed guides, enhance surgical accuracy, fostering a closer match to the original mandibular structure. Shared screw tracks between the mandibular osteotomy and fibula positioning guides simplify the procedure, further minimizing trauma and operative time ( Seruya et al., 2013 ; Schepers et al., 2015 ; Wu et al., 2021 ). Using the osteotomy guide and positioning guide, the fibula is contoured and then affixed with mini titanium plates. Shaw et al. (2004) proved that there were no significant differences in complications between miniplates and reconstruction plates, but the author also highlighted the defects of reconstruction plates, including stress shielding, interference with the vascular pedicle, and problems of metal fatigue when bending plates in the sagittal plane. In comparison, miniplates which avoid the above drawbacks are a better choice. Intermaxillary fixation was performed after surgery for 1 week, encouraging oral exercises to prevent trismus.

The vascular pedicle is severed after the recipient vessels are prepared, markedly reducing ischemic time and overall duration of the surgery. Literature indicates that when the ALT donor site width is under 8.0 cm, primary closure is feasible; for wider defects, skin grafting becomes necessary ( Chen and Tang, 2003 ). Some reports suggest that direct suturing is feasible when the width is less than 10.0 cm ( Townley et al., 2011 ). Studies have proposed that the ratio of flap width to thigh circumference can serve as a reliable metric for direct wound closure, with a ratio less than 16% indicating direct closure ( Boca et al., 2010 ). In our study, we found that for one patient, the flap width was 9.0 cm, and direct suturing did not induce fascial compartment syndrome or other complications.

While the use of double flaps allows for the repair of large composite tissue defects in the oromandibular region, overcoming the limitations of a single flap or composite flap due to vascular pedicle restrictions, it demands higher provisions for neck vessels. This includes the preparation of two sets of anastomotic arteries and veins in the recipient area. In our study, it was found that arteries were relatively easier to prepare, with a total of 16 arteries prepared. The most frequently used anastomotic arteries were the facial artery and the superior thyroid artery, while the facial vein and internal jugular vein were the most commonly used anastomotic veins. Flow-through flaps, as reported in literature ( Qing et al., 2015 ; He et al., 2021 ), allow the usage of only one set of recipient area vessels. However, this approach carries a significant drawback: if a vascular crisis arises, both flaps are in danger of necrosis. Therefore, we advocate for the preparation of two sets of anastomotic arteries and veins in the recipient area to mitigate such circumstances. Literature suggests that the ligated internal jugular vein can be utilized for end-to-side anastomosis, offering a method for venous anastomosis ( Akazawa et al., 2019 ). Furthermore, it has been reported that the transverse cervical vein and superficial temporal vein can also serve as recipient area vessels ( Hansen et al., 2007 ; Tessler et al., 2017 ; Wang et al., 2021 ).

This method affords greater flexibility and autonomy, but it involves extended operation time, high costs, considerable trauma, and numerous potential complications. It mandates superior surgical skill, restricting its broader implementation. Inexperienced medical institutions and young physicians should first master single flap reconstruction before considering advanced techniques. Without this foundation, there’s a risk of increased surgical complications and irreversible outcomes. Additionally, the inclusion of 3D printing escalates treatment costs, making this approach unfeasible for institutions lacking this technology. In our study, though every flap transplantation was triumphant, five cases did confront complications. Two cases suffered from local oral infections and gradually recovered after conservative treatments. Two patients presented with intermuscular vein thrombosis in the lower limbs, which were successfully managed with oral medication, preventing the progression to potential organ embolisms such as cardiac, pulmonary, or cerebral embolism. Additionally, two cases demonstrated a pulmonary infection, which was effectively controlled with antibiotic therapy ( Tharakan et al., 2023 ). reported postoperative complications in multi-flap surgeries to range from 26% to 50%, aligning with our findings. Earlier research indicated a 5-year survival rate for advanced head and neck cancers between 25% and 56% ( Abdelmeguid et al., 2021 ; Mody et al., 2021 ). Our study, with 2 out of 8 patients succumbing to postoperative tumor recurrence, indicates a marginally superior survival rate, albeit potentially influenced by the relatively shorter follow-up duration. In summary, our study’s outcomes resonate with existing literature, suggesting that this approach doesn’t elevate complications or mortality rates.

It is crucial to acknowledge that patients who are candidates for this procedure are typically in the advanced stages of oral cancer. As such, it is of utmost importance to strictly adhere to the surgical indications:

1) The presence of extensive composite tissue defects, including intraoral, mandibula, and extraoral tissue defects that are too extensive to be repaired with a single flap;

2) The patient must be in good physical health, without obvious surgical contraindications such as congestive heart failure, pulmonary dysfunction, or neck vessel thrombosis;

3) The tumor can be completely resectable without systemic metastasis of lung and bone tissues;

4) The patient must possess a strong desire to combat the disease, as a positive attitude towards treatment is crucial.

However, this study does have limitations. Denture restoration is crucial for patients’ masticatory function ( Sozzi et al., 2017 ). Found that implant survival was high and implant-supported prostheses were a reliable rehabilitation option in patients whose jaws have been reconstruction with fibula-free flap. In our surgical method, fibula was used to prepare for implant repair in the future. However, due to postoperative adjuvant radiotherapy, patients paid more attention to tumor treatment and neglected denture repair. Both function and aesthetics are critically important, yet there is a potential gap in patients’ understanding of these aspects. Consequently, it’s our responsibility to educate them, promoting the benefits of implant restorations to restore masticatory function. Because of the rarity of such patients, we were unable to conduct controlled studies to objectively evaluate the advantages and disadvantages of this method compared to other treatment modalities. Nonetheless, we are confident that as the number of cases increases, the effectiveness of this treatment strategy will be confirmed. Moreover, the success of the double-flap surgery heavily relies on a precise preoperative surgical design and thorough considerations. The surgical approach offers limited flexibility, and the surgical procedure cannot be changed arbitrarily during the operation, as any deviations may result in a mismatch with the original design. Should unforeseen circumstances arise intraoperatively, we are prepared to implement alternative surgical strategies. Developing methodologies to anticipate, mitigate, and adeptly respond to such occurrences will constitute a primary objective in our ongoing research endeavors.

5 Conclusion

In conclusion, VSP/3D printing assisted FOSCFs combined with ALTs offers a safe and effective avenue for reconstructing oromandibular massive composite tissue defects in the study. However, the broader benefits and efficacy of this technique necessitate further validation through an expanded patient cohort.

Data availability statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

Ethics statement

The studies involving humans were approved by the ethical committee of the Affiliated Hospital of Qingdao University. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

Author contributions

YX: Investigation, Writing–original draft. YL: Investigation, Visualization, Writing–original draft. WX: Visualization, Writing–original draft. JY: Data curation, Writing–review and editing. LX: Validation, Writing–review and editing. LL: Data curation, Writing–review and editing. ZX: Formal Analysis, Writing–review and editing. JS: Funding acquisition, Resources, Writing–review and editing.

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was funded by the Qingdao Medical and Health Research Program (grant number: 2021-WJZD193), the Qingdao University Affiliated Hospital Clinical Medicine + X Scientific Research Project (grant number: QDFY+X202101041), the Shandong Province Medical and Health Technology Development Plan Project (grant number: 202208020979), Qingdao Key Health Discipline Development Fund and Oral Medicine Climbing Discipline Project in Qingdao.

Acknowledgments

This study was approved by the ethical committee of the affiliated hospital of qingdao university (NO. QYFYWZLL 27958).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Keywords: flap transplantation, reconstructive surgery, virtual surgical planning, multipleflap, 3D printing

Citation: Xu Y, Li Y, Xiao W, Yue J, Xue L, Li L, Xu Z and Sun J (2023) Virtual surgical planning/3D printing assisted fibula osteoseptocutaneous flap combined with anterolateral thigh flaps for extensive composite oromandibular defects reconstruction: a retrospective study of case series. Front. Bioeng. Biotechnol. 11:1273318. doi: 10.3389/fbioe.2023.1273318

Received: 05 August 2023; Accepted: 23 October 2023; Published: 02 November 2023.

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Copyright © 2023 Xu, Li, Xiao, Yue, Xue, Li, Xu and Sun. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Jian Sun, [email protected]

This article is part of the Research Topic

Advanced Oral Disease Therapy: Approaches, Biotechnology, and Bioactive Materials, Volume II