Literature reviews, systematic reviews and other reviews from the family of reviews combine information from multiple studies on a particular topic to comprehensively understand their findings. This process of evidence or knowledge synthesis helps determine the effectiveness of treatments, interventions, or understand experiences related to education, health conditions or social policy. By synthesizing evidence, researchers can advance understanding, identify gaps in knowledge, establish best practices, and inform policymakers and practitioners.
The foundation of all evidence synthesis methods is literature searching. Best practice is to undertake a systematic literature search so that all publications or literature available on a topic can be synthesised for the review.
There are many different types of reviews used in evidence synthesis. This study from 2019 identified 48 review types which were categorised into seven families. The following are some of the most common review types used:
Narrative/Literature reviews: Broad perspective on topic (like a textbook chapter), no specified search strategy, significant bias issues, may not evaluate quality of evidence
Scoping Reviews: An overview of the literature on a broader topic; often done to identify whether a systematic review is feasible.
Systematic reviews: Comprehensive with minimized bias, based on specific question and criteria with a pre-planned protocol, evaluates quality of evidence
Rapid reviews: Comprehensive approach as with a systematic review but components of the systematic review process are simplified or omitted to produce information in a timely manner
Sutton A, Clowes M, Preston L, Booth A. Meeting the review family: exploring review types and associated information retrieval requirements. Health Information Libraries Journal. 2019 Sep;36(3):202-222. doi: 10.1111/hir.12276.
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Narrative/Literature Review |
Scoping Review |
Systematic Review |
Rapid Review |
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Purpose |
Summarize and present available research on a topic | Map the evidence on a topic, identify gaps, and provide an overview | Answer a specific research question by synthesizing all relevant studies | Provide a quick synthesis of evidence due to time constraints |
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Research Question |
Broad and general | Broad and exploratory | Specific and focused | Specific and focused |
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Methodology |
Informal and subjective | Systematic but less rigorous than systematic reviews | Highly systematic and rigorous often adhering to defined methodology | Systematic but with some methodological shortcuts |
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Search strategy |
Not comprehensive | Comprehensive, explicit and transparent | Comprehensive, explicit and transparent. Includes peer review of search strategy | Comprehensive but may limit search scope (e.g., timeframe, databases) |
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Bias |
Higher risk of bias due to lack of systematic approach | Lower risk of bias than narrative reviews | Minimized risk of bias through explicit and reproducible methods. Mandatory Risk of Bias Assessment | Potentially higher risk of bias due to methodological shortcuts |
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Time and resources |
Less time-consuming and resource-intensive | Moderate time and resources required | Highly time-consuming and resource-intensive | Less time-consuming than systematic reviews |
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Outcome |
General overview of the topic | Overview of the extent and nature of research, identification of gaps | Detailed and reliable synthesis of evidence. Can include meta-analysis of quantitative studies | Quick synthesis of evidence, may not be as comprehensive or reliable as systematic reviews |
