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A Guide to Evidence Synthesis

Types of Evidence Synthesis

Types of Evidence Synthesis


Evidence synthesis refers to any method of identifying, selecting, and combining results from multiple studies. A systematic review is a type of evidence synthesis. For help selecting a methodology, try our review methodology decision tree.

Other types of evidence synthesis include: 

​​Literature (Narrative) Review

  • 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 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) 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.
  • May be conducted independently or as part of a systematic review.