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Systematic reviews, scoping reviews and other evidence syntheses

Overview of evidence synthesis reviews and relevant strategies, tools and resources.

What is evidence synthesis?

Evidence synthesis:

  • also called knowledge synthesis
  • uses reproducible and transparent methods to analyze data from multiple primary studies
  • refers to evidence that has been:
    • synthesized from a large set of data/studies
    • summarized
    • critically appraised
  • synthesized evidence is considered:
    • less biased
    • more rigorous
    • more generalizable


Why do we need evidence synthesis?

  • Combining and appraising information from multiple studies:
    • helps ensure clinicians use the most appropriate treatment/medication
    • provides evidence-based information to guide health policy and programming
    • reduces unnecessary repetition of research studies

Steps in evidence synthesis

Evidence synthesis generally involves these steps: undefined

  • Stating the objectives of the research
  • Defining eligibility criteria for studies to be included and excluded
  • Identifying (all) potentially eligible studies
  • Screening for inclusion and exclusion
  • Extracting data from the final set of screened studies
  • Appraising the final set of studies
  • Applying statistical analysis, if applicable
  • Preparing a structured report of the research

Reference: CIHR. (n.d.) A knowledge synthesis chapter: Stages of knowledge synthesis

Image: Ayala, P. (2020). Screening for studies in systematic reviews, scoping reviews, and other knowledge syntheses: Strategies for improvement. KSIG webinar, April 2020.

Types of evidence synthesis reviews

  • There are multiple types of synthesis reviews
  • It's important to:
    • select the appropriate review method for your research question
    • be transparent and clear about your aims, methods, and reporting
  • This diagram from Yale Library illustrates some of the questions to consider when deciding on a review type:




Centre for Research Evaluation, London School Hygiene and Tropical Medicine. (n.d.) Evidence synthesis: synthesis methods.

Sutton, A., Clowes, M., Preston, L., & Booth, A. (2019). Meeting the review family: exploring review types and associated information retrieval requirements. Health Information & Libraries Journal, (3), 202.