How to Write a Systematic Literature Review: A 6-Step Guide to Conducting a Systematic Review

Understanding the Systematic Literature Review Process

What is a Systematic Literature Review?

• Definition: A systematic literature review (SLR) is a structured and methodical approach to reviewing and synthesizing evidence from existing research on a specific topic.
• Purpose: The goal of a systematic literature review is to summarize evidence-based findings, ensuring that the conclusions are comprehensive and reliable.
• Process: This review involves a rigorous process where studies are identified through comprehensive search strategies, and then assessed using predefined criteria for inclusion and exclusion.
• Methodology: It follows a methodological approach, making the review process transparent, repeatable, and reproducible.
• Outcome: The systematic literature review aims to provide a high-quality synthesis of the available evidence and assess the strength of the studies included.

Importance of Conducting a Systematic Literature Review

• Comprehensive Analysis: A systematic literature review allows researchers to appraise existing studies, ensuring that no significant research is overlooked.
• Evidence-Based: By relying on a systematic process, the review is evidence-based, drawing conclusions from the best available data.
• Avoids Bias: Unlike traditional reviews, a systematic literature review minimizes bias by following a clear, predefined protocol and search strategies.
• Informed Decision-Making: A systematic literature review helps policymakers, practitioners, and scholars make informed decisions based on consolidated, high-quality evidence.
• Meta-Analysis Inclusion: In some cases, a systematic literature review includes a meta-analysis, which quantitatively synthesizes data from various studies to generate overall trends or conclusions.
• Improves Methodology: It can improve the methodological quality of research by identifying gaps and inconsistencies in the existing literature.
• PRISMA Compliance: The PRISMA checklist helps ensure that systematic reviews meet rigorous standards for transparency and reproducibility.

Key Components of a Systematic Review

• Database Selection: One of the first steps in a systematic literature review is selecting appropriate databases to search for studies. Databases like PubMed, Scopus, and Google Scholar are commonly used.
• Search Strategies: Developing effective search strategies is crucial to ensure comprehensive data collection. This includes defining search terms, inclusion/exclusion criteria, and the types of studies to include.
• Study Selection: A systematic process is followed to screen studies based on inclusion and exclusion criteria. This ensures that only relevant and high-quality studies are included in the review.
• Appraisal: Each study is critically appraised for quality and relevance to ensure that only the best evidence is included in the review.
• Synthesis: The core of a systematic literature review is the synthesis of the findings from the included studies. This involves organizing and summarizing results in a clear, coherent manner.
• Qualitative and Quantitative Synthesis: Depending on the nature of the studies, the synthesis can be qualitative, where themes or trends are identified, or quantitative, where a meta-analysis may be conducted to aggregate numerical data.
• Review and Meta-Analysis: A systematic literature review can culminate in a review and meta-analysis, combining both qualitative insights and quantitative analyses from multiple studies.
• PRISMA Checklist: The PRISMA checklist serves as a comprehensive tool for ensuring that every stage of the systematic literature review process is transparent, methodical, and reproducible.

By following these structured components, a systematic literature review helps create a reliable, evidence-based summary of existing research that can be used to guide further studies or inform policy and practice.

A 6 Step-by-Step Guide to Conduct a Systematic Literature Review

Step 1: Defining the Research Question

• Formulate a Clear Research Question: The first step in conducting a systematic literature review (SLR) is to define a specific, clear research question. This question will guide the entire review process. A well-defined question helps focus the search for relevant studies.
• Utilize Review Types: The research question should align with the type of review being conducted, whether it’s a scoping review, systematic review, or traditional literature review. It should address a gap in current literature.
• Types of Research: The research question should take into account the types of research to include, such as randomized controlled trials, qualitative studies, or observational research, depending on the field of study.
• Consider Systematic Review and Evidence: The question should be structured to address systematic reviews and meta-analyses, ensuring that it is broad enough to encompass all relevant research studies while being specific enough to avoid unnecessary data.
• Use a Framework: Tools like the PICO(T) framework (Population, Intervention, Comparison, Outcome) can help guide the formulation of the research question. This approach is particularly useful for systematic reviews in medicine.

Step 2: Developing a Review Protocol

• Creating a Structured Protocol: Developing a review protocol is crucial for a systematic literature review as it outlines the methods, criteria, and plan for conducting the review. This protocol ensures consistency throughout the review process.
• Preferred Reporting Items for Systematic Reviews (PRISMA): Use the PRISMA statement or the PRISMA 2020 statement as a guideline to develop a protocol. It ensures that the review follows a structured, evidence-based methodology.
• Search Strategy Design: The review protocol should include a detailed plan for the systematic search and the types of databases (e.g., Web of Science, library guides, university library) to be used. It also outlines the systematic review methods to search for relevant studies and how to handle grey literature.
• Clarifying the Inclusion/Exclusion Criteria: The protocol should clearly define the criteria for study selection, including the types of systematic reviews to include and the types of literature (e.g., research literature, social science articles, or Cochrane reviews).
• Flow Diagram: Create a flow diagram to visually represent the review process, helping to map out the selection process and ensure transparency in your review conduct.

Step 3: Conducting a Systematic Literature Search

• Handling Grey Literature: Grey literature may not be indexed in major databases, but it is crucial to include it for a comprehensive review. Search for grey literature sources such as theses, government reports, and publications from research institutions.
• Systematic Search: The systematic search is the backbone of the systematic literature review. It requires using pre-determined search strategies to retrieve a comprehensive set of studies from relevant databases such as Web of Science, Google Scholar, or university library databases.
• Library Guides: Consult library guides for assistance in searching specific databases and using relevant keywords, such as “systematic reviews” or “systematic literature review,” to ensure that the search captures all pertinent literature.
• Use of Relevant Databases: Make sure to use multiple databases to ensure a comprehensive search. This includes academic databases like PubMed, Scopus, and Cochrane Reviews, along with grey literature such as reports, theses, and conference papers.
• Keywords and Search Terms: Ensure that the search terms used are broad enough to capture all relevant studies, but specific enough to avoid irrelevant articles. Consider including research findings, types of research, and specific keywords related to the review question.

Step 4: Selecting Studies for Inclusion

• Screening and Inclusion Criteria: Once you have gathered a pool of studies, the next step in your systematic literature review is to apply inclusion and exclusion criteria to select studies that meet your research question. This process helps critically appraise existing research and ensures that only high-quality studies are included.
• Types of Reviews and Associated Criteria: Depending on the type of review being conducted, you will have specific inclusion criteria, such as study type (e.g., randomized controlled trials) or study quality (e.g., ensuring the study is not biased).
• Review Method Selection: In a systematic review, selecting relevant studies involves reviewing each study’s methodological quality, ensuring the studies have a robust design and relevance to your research question.
• Systematic Way: Apply a systematic way to select studies, ensuring transparency in how decisions are made. The use of a flow diagram is helpful in visualizing and reporting the selection process.
• Types of Literature: Make sure to include both traditional literature and systematic reviews or meta-analyses. This ensures that the review is comprehensive and includes all relevant research studies.

Step 5: Data Extraction and Analysis

• Data Extraction: Extract key information from each selected study, such as the study design, outcomes, sample size, and statistical methods. This step helps organize the data for further analysis.
• Synthesize Data: The data extraction process will lead to the synthesis of the data. In a systematic literature review, this often involves both qualitative and quantitative synthesis, depending on the nature of the studies being reviewed.
• Meta-Analysis: If applicable, a meta-analysis may be conducted to statistically combine the results of studies, providing a summary of findings across studies. This is often done in fields like medicine, where systematic reviews in medicine are prevalent.
• Appraising the Quality of Studies: Appraise the quality of the studies being analyzed using appropriate criteria. This ensures that only robust and credible research is included in the final synthesis.
• Use of Software Tools: Use software tools to manage and analyze data from studies. Tools like EndNote or Covidence help organize references and assist with the systematic review process.

Step 6: Reporting the Systematic Literature Review Findings

• Reporting the Findings: Once the data has been analyzed and synthesized, the final step is to report the findings in a clear, comprehensive manner. This is where the findings from your systematic literature review are communicated to the research community.
• PRISMA Statement: Follow the PRISMA statement to structure your review report. The PRISMA statement ensures that your review adheres to standardized reporting practices and includes all necessary elements for transparency and reproducibility.
• Discussing Findings and Future Research: In your report, discuss the findings in relation to the current literature and identify gaps for future research. Highlight any types of research that need further exploration or improvement.
• Types of Systematic Reviews: Depending on the types of systematic reviews conducted, the report should clearly differentiate between qualitative and quantitative findings, including whether a meta-analysis was conducted.
• Conclusion: Conclude with a summary of the main findings from the systematic literature review and how they contribute to the existing body of knowledge in the field.

By following these six steps, you can effectively conduct and report a systematic literature review, ensuring a comprehensive, transparent, and evidence-based summary of the existing research on your chosen topic.

Best Practices in Writing a Systematic Literature Review

Writing the Introduction and Methodology Sections

• Introduction: The introduction of a systematic literature review should clearly define the research question and the scope of the review. It should provide an overview of the relevant literature and highlight the importance of the review in contributing to the field.
  • Formulate Research Questions: Formulate a clear, focused research question that guides the entire review process. The question should be broad enough to encompass various studies but specific enough to yield meaningful results.
  • Types of Literature Review: Specify the type of literature review (e.g., systematic review, scoping review) and the criteria for selecting the studies to be included.
  • Contextualize the Review: Set the context by explaining why the systematic literature review is being conducted and how it fits into the larger body of research on the topic.
• Methodology: The methodology section outlines the systematic review methods and the steps taken to gather, evaluate, and analyze the data.
  • Systematic Search: Clearly describe the systematic search process, including the databases and search strategies used to identify relevant studies. This includes the inclusion and exclusion criteria, ensuring transparency in the conduct of the review.
  • Data Extraction: Detail the data extraction process and the use of management tools for handling the studies. Mention how studies are appraised for quality and relevance, using tools such as the PRISMA checklist.
  • Review Types and Associated Criteria: Explain how different review types and associated methodologies were applied to evaluate the studies.

Organizing the Results and Discussion

• Organizing the Results: In the results section, you should provide a clear summary of the findings from the studies included in the systematic literature review. Present the data in an organized manner to show patterns, trends, and key findings.
  • Synthesize the Data: The synthesis should include both qualitative and quantitative summaries, depending on the type of data. For example, a meta-analysis may be included for studies with statistical data.
  • Types of Research: Categorize the findings by types of research or study design (e.g., randomized controlled trials, observational studies) to allow readers to easily compare results.
  • Quality and Quantity of Literature: Discuss the quantity and quality of literature included in the review. This helps assess the overall strength of the evidence base.
• Discussion: The discussion section interprets the results and places them in the context of the current literature.
  • Understand Systematic Reviews: Provide an understanding of systematic reviews by comparing your findings with previous research, identifying trends or contradictions.
  • Implications: Discuss the implications of the results for practice, policy, and future research. Explain how the findings contribute to the field and suggest areas where further research is needed.
  • Limitations: Acknowledge any limitations of the systematic literature review, such as potential biases in study selection or gaps in the evidence.

Concluding the Systematic Literature Review

• Summarizing Key Findings: In the conclusion, summarize the key findings from your systematic literature review. Restate the importance of the review and its contributions to the field.
  • Systematic Review Uses: Highlight the systematic review uses and how the findings can influence future research, policy decisions, or practical applications.
  • Practical Applications: Provide recommendations for practitioners or policymakers based on the findings. Discuss how the review’s findings can be applied in real-world settings.
• Recommendations for Future Research: Conclude by suggesting areas for future research that may fill gaps identified during the review.
  • Conducting Systematic Literature: Emphasize the importance of conducting systematic literature reviews in the field. Encourage further studies that build upon the existing evidence base and improve the understanding of the topic.
  • Systematic Reviews Are Conducted: Reiterate that systematic reviews are conducted to ensure that the most relevant, high-quality research is included in the review process.

Managing the Systematic Literature Review Process as a Research Methodology

Using Systematic Review Management Software

• Streamlining Data Organization: Systematic review management software is essential for efficiently organizing and managing the vast amount of data involved in a systematic literature review. This software helps researchers handle references, track studies, and ensure that no relevant research is overlooked.
  • Managing Citations: Software tools like EndNote or Rayyan help researchers manage citations, screen studies, and categorize the data for easy retrieval and analysis during the conduct of a review.
  • Evidence Synthesis: These tools also support the evidence syntheses process by allowing researchers to systematically extract, appraise, and synthesize data from multiple studies, ensuring a comprehensive and rigorous review.
  • Streamlining Workflow: By automating parts of the review process, software can help reduce the burden of manual tasks such as data entry, study selection, and tracking revisions, thus increasing the overall efficiency of a systematic literature review.

Streamlining Your Review Process

• Improved Collaboration: Systematic review management software facilitates collaboration between multiple researchers, enabling teams to work together on different stages of the review process, such as writing a literature review, extracting data, and drafting sections of the report.
  • Tracking Progress: The software can help in tracking the status of the review, showing which studies have been included, excluded, or are under review, thus ensuring that no part of the systematic literature review process is overlooked.
  • Standardized Protocol: Using management tools ensures that all stages of the review are conducted according to a standardized protocol, including predefined inclusion/exclusion criteria, which is essential for maintaining the quality and reproducibility of the review process.
  • Reporting in Systematic Reviews: Many of these tools come with features for reporting systematic reviews, helping researchers structure their findings according to established guidelines, such as the PRISMA statement, which includes all necessary items for reporting in systematic reviews.

Tracking and Monitoring Progress

• Monitoring Workflow: Systematic review management software offers tracking features to monitor the progress of the systematic literature review. This includes tracking which studies are still pending, completed, or in the process of extraction or analysis.
  • Project Milestones: By setting project milestones, you can ensure that the review progresses smoothly, with clear deadlines for each phase of the process, from the review of the literature to the final synthesis of the findings.
  • Progress Reports: The software generates reports to keep all team members updated on the status of the review. This also helps identify any bottlenecks in the process, allowing for prompt action to maintain the review’s timeline.
  • Ensuring Comprehensive Coverage: Tracking tools also help ensure the review is comprehensive, capturing all relevant studies and research on the topic. This supports the goal of the systematic literature review to synthesize all available evidence, ensuring the conduct of a review is thorough and reliable.

By utilizing systematic review management software, researchers can streamline the process, stay organized, and maintain high standards of transparency and rigor, ensuring the systematic literature review process is both efficient and effective.

Common Challenges in Systematic Literature Reviews and How to Overcome Them in Systematic Review Methodology

Handling Large Volumes of Data

• Challenge: One of the main difficulties when conducting a systematic literature review is managing the large volumes of data collected from multiple studies. The process can become overwhelming, especially when there are numerous relevant studies to analyze and synthesize.
  • Solution: To handle large data sets effectively, utilize systematic review management software to organize references and streamline the data extraction process. This software can automate citation management and help track progress across different stages of the review.
  • Comprehensive Systematic Search: Ensure that the systematic search is comprehensive but well-defined. Narrowing search terms and using filters in databases will help focus on the most relevant studies, reducing the overall volume of data while maintaining inclusivity.
  • Database Organization: Organize the data into categories (e.g., by study design, outcome measures, or methodological approach) to make it easier to compare studies, spot trends, and identify gaps in the literature.

Dealing with Bias and Ensuring Objectivity

• Challenge: Bias can creep into the systematic literature review process, whether through subjective selection of studies, preferential reporting, or unintentional omission of key research. Maintaining objectivity is crucial to ensuring the integrity of the review.
  • Solution: Adhere to predefined inclusion and exclusion criteria. A transparent, systematic approach will help minimize bias during the selection process.
  • Typology of Reviews: Understanding different typology of reviews can help guide the methodology. For example, distinguishing between a systematic review and a traditional literature review can clarify which studies should be prioritized and how to avoid cherry-picking studies.
  • Use of PRISMA Guidelines: Incorporate the PRISMA guidelines or similar reporting standards for transparency. By following established standards for reporting systematic reviews, you ensure that your review is rigorous, reproducible, and unbiased.
  • Peer Review: Having independent reviewers involved in the process can reduce the likelihood of bias. This also provides a second opinion on study selection and data extraction.

Addressing Inconsistent or Poor-Quality Studies

• Challenge: Another common challenge in systematic literature reviews is dealing with studies of varying quality. Inconsistent methodologies, sample sizes, and reporting standards can make it difficult to synthesize the evidence.
  • Solution: Critically appraise each study for its methodological quality. Studies with poor quality should be reported but noted as having limitations in your review.
  • Conducting an SLR: The systematic review methodology includes setting criteria for the quality of included studies. Ensure that only studies meeting specific quality benchmarks are included in the systematic literature review. This might involve assessing the reliability of data sources, sample sizes, and research designs.
  • Evidence Syntheses: When synthesizing evidence from lower-quality studies, it is essential to explain the impact of study quality on the overall findings. Acknowledge when studies have methodological flaws and consider this in your conclusions.
  • Use of Sensitivity Analysis: Conducting sensitivity analyses can help determine how the inclusion or exclusion of low-quality studies affects the final conclusions of your systematic literature review.

By anticipating and addressing these challenges, researchers can improve the quality and reliability of their systematic literature review and ensure a rigorous, comprehensive analysis of the topic under investigation.