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Evidence Syntheses: Types of Evidence Synthesis

Methodology Decision Making Tool

Evidence synthesis refers to any method of identifying, selecting, and combining results from multiple studies. A systematic review is a type of evidence synthesis. There are several other types of evidence syntheses - the first step in undertaking one is ensuring you are choosing the correct methodology. Utilize this decision making tool to ensure you are choosing the correct type of evidence synthesis! (from Cornell University Library, CC-BY License 4.0).

Descriptions of Evidence Syntheses

Literature Review (Narrative): A broad term referring to reviews with a wide scope and non-standardized methodology.

  • Search strategies, comprehensiveness, and time range covered vary and do not follow an established protocol.

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.
  • See Evidence summaries: the evolution of a rapid review approach for methodological guidance.

Scoping Review or Systematic Map: Systematically and transparently collects and categorizes existing evidence on a broad topic or set of research questions.

  • Seeks to identify research gaps and opportunities for evidence synthesis.
  • May critically evaluate existing evidence, but does not attempt to synthesize the results in the way a systematic review would.
  • May take longer than a systematic review.
  • See Scoping studies: towards a methodological framework for methodological guidance.
  • See Environmental Evidence Journal Systematic Maps and Guidance on Systematic Maps—CIFOR.

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.

Systematic Review: A methodical and comprehensive literature synthesis focused on a well-formulated research question.

  • Aims to identify and synthesize all of the scholarly research on a particular topic, including both published and unpublished studies.
  • Conducted in an unbiased, reproducible way to provide evidence for practice and policy-making and to identify gaps in research.
  • May involve a meta-analysis.
  • Much more time-intensive than traditional literature reviews.

Meta-Analysis: A 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.


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