Systematic Reviews & Evidence Synthesis Methods

Evidence synthesis refers to any method of identifying, selecting, and combining results from multiple studies. For help selecting a methodology, please refer to:

Types of evidence synthesis include: 

​​Systematic Review

• Systematically and transparently collect and categorize existing evidence on a broad question of scientific, policy or management importance
• Compares, evaluates, and synthesizes evidence in a search for the effect of an intervention
• Time-intensive and often take months to a year or more to complete
• The most commonly referred to type of evidence synthesis. Sometimes confused as a blanket term for other types of reviews

Systematized Literature Review

• Not a true evidence synthesis review, but employs certain elements of a systematic review
• No specific methodology; does not require a protocol or critical appraisal of the evidence
• Conducted by only 1 or 2 people
• May be completed in about 2-6 months

​​Literature (Narrative) Review

• Not a true evidence synthesis review, but a broad term referring to reviews with a wide scope and non-standardized methodology
• Search strategies, comprehensiveness, and time range covered will vary and do not follow an established protocol

​Scoping Review or Evidence Map

• Systematically and transparently collect and categorize existing evidence on a broad question of scientific, policy or management importance
• Seeks to identify research gaps and opportunities for evidence synthesis rather than searching for the effect of an intervention
• May critically evaluate existing evidence, but does not attempt to synthesize the results in the way a systematic review would.(see EE Journal and CIFOR)
• May take longer than a systematic review
• See Arksey and O'Malley (2005) or Peters et al (2020) for methodological guidance

​Rapid Review

• Applies Systematic Review methodology within a time-constrained setting
• Employs methodological "shortcuts" (limiting search terms for example) at the risk of introducing bias
• Useful for addressing issues needing quick decisions, such as developing policy recommendations
• See Evidence Summaries: The Evolution of a Rapid Review Approach

Umbrella Review

• Reviews other systematic reviews on a topic
• Often defines a broader question than is typical of a traditional systematic review
• Most useful when there are competing interventions to consider

Meta-analysis

• Statistical technique for combining the findings from disparate quantitative studies
• Uses statistical methods to objectively evaluate, synthesize, and summarize results
• Conducted as an additional step of a systematic review

From Cornell University Library's Evidence Synthesis guide.