Systematic Literature Review
A systematic literature review is a structured, transparent, and reproducible method for identifying, selecting, critically appraising, and synthesizing research relevant to a focused question. It relies on predefined review protocols, explicit inclusion and exclusion criteria, and comprehensive search strategies to reduce selection bias and improve consistency. Included studies are usually assessed for methodological quality or risk of bias before their findings are synthesized narratively or, when appropriate, statistically through meta-analysis. The method is used to consolidate cumulative evidence, identify patterns and gaps in the literature, and support robust scholarly or policy conclusions.
Page et al. (2021) provide the most up-to-date high-level methodological guidance for systematic reviews through the PRISMA 2020 framework, refining standards for transparency, completeness, and reproducibility. Moher et al. (2009) established PRISMA as the dominant reporting framework for systematic reviews and meta-analyses, formalizing the checklist and flow diagram that continue to structure review practice. Mulrow (1994) is an early foundational methodological paper that articulated the rationale for systematic reviews and emphasized the need for explicit, comprehensive, and bias-reducing review procedures.
Key references
Page, M. J., McKenzie, J. E., Bossuyt, P. M., Boutron, I., Hoffmann, T. C., Mulrow, C. D., Shamseer, L., Tetzlaff, J. M., Akl, E. A., Brennan, S. E., Chou, R., Glanville, J., Grimshaw, J. M., Hróbjartsson, A., Lalu, M. M., Li, T., Loder, E. W., Mayo-Wilson, E., McDonald, S., ... Moher, D. (2021). The PRISMA 2020 statement: An updated guideline for reporting systematic reviews. Systematic Reviews, 10(1), Article 89. https://doi.org/10.1186/s13643-021-01626-4
Moher, D., Liberati, A., Tetzlaff, J., Altman, D. G., & The PRISMA Group. (2009). Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement. PLoS Medicine, 6(7), Article e1000097. https://doi.org/10.1371/journal.pmed.1000097
Mulrow, C. D. (1994). Rationale for systematic reviews. BMJ, 309(6954), 597-599. https://doi.org/10.1136/bmj.309.6954.597
Qualitative Evidence Synthesis
Qualitative evidence synthesis is a family of systematic review approaches that integrates findings from primary qualitative studies to generate richer, cumulative interpretations of experiences, meanings, beliefs, and contextual influences. It is used to answer questions about how and why phenomena occur, how interventions are experienced, and what shapes acceptability, feasibility, implementation, and equity. The method applies transparent and systematic procedures for question formulation, searching, selection, appraisal, extraction, and synthesis, while preserving the interpretive character of qualitative inquiry. Depending on the synthesis approach selected, it may aggregate findings, develop higher-order themes or concepts, or generate new theoretical understandings that inform research, practice, and policy.
Flemming and Noyes (2021) provide the most up-to-date overarching methodological account of qualitative evidence synthesis, clarifying its scope, purposes, core processes, and standards for rigor and reporting. Flemming, Booth, Garside, Tunçalp, and Noyes (2019) offer influential practical guidance on matching qualitative evidence synthesis designs and methods to complex interventions and guideline development needs. Dixon-Woods et al. (2006) remains a foundational early paper because it articulated the epistemological and methodological challenges of incorporating qualitative research into systematic reviews, helping establish the rationale for distinct qualitative evidence synthesis methods.
Key references
Flemming, K., & Noyes, J. (2021). Qualitative evidence synthesis: Where are we at? International Journal of Qualitative Methods, 20, 1609406921993276. https://doi.org/10.1177/1609406921993276
Flemming, K., Booth, A., Garside, R., Tunçalp, Ö., & Noyes, J. (2019). Qualitative evidence synthesis for complex interventions and guideline development: Clarification of the purpose, designs and relevant methods. BMJ Global Health, 4(Suppl. 1), e000882. https://doi.org/10.1136/bmjgh-2018-000882
Dixon-Woods, M., Bonas, S., Booth, A., Jones, D. R., Miller, T., Sutton, A. J., Shaw, R. L., Smith, J. A., & Young, B. (2006). How can systematic reviews incorporate qualitative research? A critical perspective. Qualitative Research, 6(1), 27-44. https://doi.org/10.1177/1468794106058867
Meta-synthesis
Meta-synthesis is a qualitative research synthesis method that systematically interprets and integrates findings from multiple qualitative studies addressing a related phenomenon. Rather than statistically aggregating results, it compares concepts, themes, and interpretations across studies to generate higher-order insights, conceptual models, or theory. The method is typically iterative and involves searching for relevant studies, selecting and appraising them, closely reading findings, comparing interpretations, and synthesizing them into a new interpretive account. Its aim is to move beyond the conclusions of individual studies while remaining grounded in the meanings and contexts reported in the original research.
Bondas and Hall (2007) provide the most recent seminal methodological guidance among these core works by clarifying the major challenges of meta-synthesis and emphasizing its interpretive, theory-building purpose. Walsh and Downe (2005) offer a widely cited methodological review that defines meta-synthesis, outlines its stages, and distinguishes it from quantitative meta-analysis by stressing its interpretive rather than aggregative logic. Sandelowski, Docherty, and Emden (1997) remain foundational because they articulated the early methodological issues and techniques of qualitative meta-synthesis and established the need to turn an accumulation of qualitative studies into cumulative understanding.
Key references
Bondas, T., & Hall, E. O. C. (2007). Challenges in approaching metasynthesis research. Qualitative Health Research, 17(1), 113-121. https://doi.org/10.1177/1049732306295879
Walsh, D., & Downe, S. (2005). Meta-synthesis method for qualitative research: A literature review. Journal of Advanced Nursing, 50(2), 204-211. https://doi.org/10.1111/j.1365-2648.2005.03380.x
Sandelowski, M., Docherty, S., & Emden, C. (1997). Focus on qualitative methods. Qualitative metasynthesis: Issues and techniques. Research in Nursing & Health, 20(4), 365-371. https://doi.org/10.1002/(SICI)1098-240X(199708)20:4%3C365::AID-NUR9%3E3.0.CO;2-E
Meta-ethnography is an interpretive method for synthesizing findings from qualitative studies by comparing and translating concepts, themes, and metaphors across studies. Rather than aggregating results, it aims to generate a new conceptual interpretation that goes beyond the findings of any single primary study. The method is commonly described through seven iterative phases, including selecting relevant studies, reading them closely, determining how they relate, translating them into one another, and building a higher-order synthesis. A central goal is to preserve the meaning and context of the original studies while producing reciprocal, refutational, and line-of-argument syntheses where appropriate.
France et al. (2019) provide the most up-to-date seminal guidance, extending meta-ethnography through the eMERGe framework and offering explicit criteria that guide transparent conduct and reporting across all seven phases. Britten et al. (2002) supplied one of the earliest and most influential worked examples, showing how the method could be operationalized in applied qualitative synthesis and making the approach usable for later reviewers. Noblit and Hare (1988) established the method itself, defining the interpretive logic of translation, comparison, and line-of-argument synthesis that continues to underpin meta-ethnographic work.
Key references
France, E. F., Cunningham, M., Ring, N., Uny, I., Duncan, E. A. S., Jepson, R. G., Maxwell, M., Roberts, R. J., Turley, R. L., Booth, A., Britten, N., Flemming, K., Gallagher, I., Garside, R., Hannes, K., Lewin, S., Noblit, G. W., Pope, C., Thomas, J., . . . Noyes, J. (2019). Improving reporting of meta-ethnography: The eMERGe reporting guidance. BMC Medical Research Methodology, 19(1), 25. https://doi.org/10.1186/s12874-018-0600-0
Britten, N., Campbell, R., Pope, C., Donovan, J., Morgan, M., & Pill, R. (2002). Using meta ethnography to synthesise qualitative research: A worked example. Journal of Health Services Research & Policy, 7(4), 209-215. https://doi.org/10.1258/135581902320432732
Noblit, G. W., & Hare, R. D. (1988). Meta-ethnography: Synthesizing qualitative studies. SAGE. https://doi.org/10.4135/9781412985000
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Narrative Synthesis
Narrative synthesis is a method for systematically integrating findings from multiple studies primarily through words and text rather than statistical pooling. It is especially appropriate when included studies are too heterogeneous in design, intervention, outcome, or context for meta-analysis to be suitable. The method typically develops a structured account of the evidence by producing a preliminary synthesis, exploring patterns and relationships across studies, and assessing the robustness of the conclusions. Its aim is to generate a transparent, theoretically informed interpretation of the evidence while preserving attention to context, complexity, and variation.
Lisy and Porritt (2016) provide a concise contemporary methodological overview of narrative synthesis, clarifying when the method is appropriate and highlighting its main practical and interpretive challenges. Rodgers et al. (2009) extended the method by empirically testing guidance-led narrative synthesis against meta-analysis, showing how the framework can support transparent and reproducible review conclusions. Popay et al. (2006) remains the foundational guidance text, defining narrative synthesis as a text-based approach to systematic review and setting out its core elements for conducting the method.
Key references
Lisy, K., & Porritt, K. A. (2016). Narrative synthesis: Considerations and challenges. International Journal of Evidence-Based Healthcare, 14(4), 201-207. https://doi.org/10.1097/01.XEB.0000511348.97198.8c
Rodgers, M., Sowden, A., Petticrew, M., Arai, L., Roberts, H., Britten, N., & Popay, J. (2009). Testing methodological guidance on the conduct of narrative synthesis in systematic reviews: Effectiveness of interventions to promote smoke alarm ownership and function. Evaluation, 15(1), 49-73. https://doi.org/10.1177/1356389008097871
Popay, J., Roberts, H., Sowden, A., Petticrew, M., Arai, L., Rodgers, M., Britten, N., Roen, K., & Duffy, S. (2006). Guidance on the conduct of narrative synthesis in systematic reviews: A product from the ESRC Methods Programme (Version 1). ESRC Methods Programme. https://doi.org/10.13140/2.1.1018.4643
Integrative Review
An integrative review is a form of knowledge synthesis that systematically gathers, appraises, and integrates evidence from diverse empirical and theoretical sources on a defined topic. Unlike review methods restricted to particular study designs, it can include quantitative, qualitative, mixed-methods, and conceptual literature within one analytic framework. Its purpose is to generate a more comprehensive understanding of a phenomenon, clarify concepts, identify gaps, and develop implications for research, policy, or practice. The method typically involves problem identification, literature searching, data evaluation, data analysis, and presentation of the synthesized findings.
Torraco (2016) provides the most recent seminal methodological guidance, framing the integrative review as a distinctive form of review research that uses existing literature to generate new knowledge and outlining principles for organizing and writing such reviews. Whittemore and Knafl (2005) remain the central methodological reference in health and applied research, clearly distinguishing the integrative review from other review types and specifying a rigorous five-stage process for conducting it. Cooper (1982) offers the earlier foundational framework for integrative research reviews, establishing core stages and scientific principles that influenced later method development.
Key references
Torraco, R. J. (2016). Writing integrative literature reviews: Using the past and present to explore the future. Human Resource Development Review, 15(4), 404-428. https://doi.org/10.1177/1534484316671606
Whittemore, R., & Knafl, K. (2005). The integrative review: Updated methodology. Journal of Advanced Nursing, 52(5), 546-553. https://doi.org/10.1111/j.1365-2648.2005.03621.x
Cooper, H. M. (1982). Scientific guidelines for conducting integrative research reviews. Review of Educational Research, 52(2), 291-302. https://doi.org/10.3102/00346543052002291
Scoping Review
A scoping review is a form of evidence synthesis used to map the breadth, nature, and distribution of research on a topic. It is designed to clarify key concepts, definitions, types of evidence, and knowledge gaps, especially in areas that are heterogeneous, emerging, or not yet amenable to a narrowly focused systematic review. The method typically uses systematic and transparent search, selection, and charting procedures to describe what evidence exists rather than to answer a highly specific effect question. Findings are usually presented as a descriptive or thematic map of the literature, with critical appraisal optional depending on the review objective.
Peters et al. (2020) provide the most up-to-date widely used methodological guidance, refining JBI-based procedures for review objectives, eligibility criteria, evidence charting, and synthesis in scoping reviews. Levac, Colquhoun, and O'Brien (2010) advanced the method by clarifying each review stage, emphasizing an iterative team-based process, and strengthening the role of purpose and stakeholder consultation. Arksey and O'Malley (2005) established the foundational framework for scoping studies, defining the core stages that continue to underpin contemporary scoping review practice.
Key references
Peters, M. D. J., Marnie, C., Tricco, A. C., Pollock, D., Munn, Z., Alexander, L., McInerney, P., Godfrey, C. M., & Khalil, H. (2020). Updated methodological guidance for the conduct of scoping reviews. JBI Evidence Synthesis, 18(10), 2119-2126. https://doi.org/10.11124/JBIES-20-00167
Levac, D., Colquhoun, H., & O'Brien, K. K. (2010). Scoping studies: Advancing the methodology. Implementation Science, 5, 69. https://doi.org/10.1186/1748-5908-5-69
Arksey, H., & O'Malley, L. (2005). Scoping studies: Towards a methodological framework. International Journal of Social Research Methodology, 8(1), 19-32. https://doi.org/10.1080/1364557032000119616
Rapid Review
Rapid review is a form of evidence synthesis that adapts systematic review methods to produce timely answers for policy, clinical, or service decisions when decision-makers face constrained timelines. It retains core systematic features such as a structured question, explicit eligibility criteria, and transparent reporting, but streamlines selected steps to accelerate completion. Common shortcuts include limiting databases, date ranges, languages, screening procedures, data extraction, critical appraisal, or synthesis depth according to the review’s purpose and deadline. The method aims to balance timeliness and rigor, with the expectation that abbreviated methods are explicitly justified and reported because they can influence comprehensiveness, certainty, and risk of bias.
Garritty et al. (2024) provide the most up-to-date methodological guidance, refining Cochrane recommendations, clarifying defining features, and emphasizing tailored, iterative choices in the design and conduct of rapid reviews. Garritty et al. (2021) established the widely used interim guidance that organized rapid review decision points across major review stages and became a central methodological benchmark for the field. Khangura et al. (2014) remains a foundational early methods paper, framing rapid review as an emerging evidence-synthesis approach and demonstrating how transparent methodological streamlining can support real-world health decision making.
Key references
Garritty, C., Hamel, C., Trivella, M., Gartlehner, G., Nussbaumer-Streit, B., Devane, D., Kamel, C., Griebler, U., & King, V. J. (2024). Updated recommendations for the Cochrane rapid review methods guidance for rapid reviews of effectiveness. BMJ, 384, e076335. https://doi.org/10.1136/bmj-2023-076335
Garritty, C., Gartlehner, G., Nussbaumer-Streit, B., King, V. J., Hamel, C., Kamel, C., Affengruber, L., & Stevens, A. (2021). Cochrane Rapid Reviews Methods Group offers evidence-informed guidance to conduct rapid reviews. Journal of Clinical Epidemiology, 130, 13-22. https://doi.org/10.1016/j.jclinepi.2020.10.007
Khangura, S., Polisena, J., Clifford, T. J., Farrah, K., & Kamel, C. (2014). Rapid review: An emerging approach to evidence synthesis in health technology assessment. International Journal of Technology Assessment in Health Care, 30(1), 20-27. https://doi.org/10.1017/S0266462313000664