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Systematic Reviews: How-To in Detail

The Whats and Whys of Protocols

Systematic reviews and scoping reviews should have a protocol which helps to plan and outline the study methodology. The protocol should include:

  • the rationale for the review
  • key questions broken into PICO (or other structured research question) components
  • inclusion/exclusion criteria
  • literature searches for published/unpublished literature
  • data abstraction/data management
  • assessment of methodological quality/risk of bias of individual studies (not required for scoping reviews)
  • data synthesis
  • grading the evidence for each key question

Why should you complete a protocol?

  • A protocol is your planning document and roadmap for the project. It allows you to complete a systematic review efficiently and accurately, ensures greater understanding among team members, and makes writing the manuscript far easier.
  • Many journals now require submitted systematic reviews to have registered protocols.
  • The PRISMA Reporting Standard lists information about the systematic review protocol as an "essential element" (PRISMA 2020 Item 24)
  • The Cochrane Handbook, The Institute of Medicine Standards, and others, all list completing a protocol as one of the important steps to a successful systematic review.

Inclusion / Exclusion Criteria

A well-defined research question will help generate the list of inclusion and exclusion criteria.

Common inclusion/exclusion criteria for systematic reviews include:

  • time frame of the outcome measurement
  • definitions for the population
  • study setting
  • geographic locations the studies are conducted in
  • language of the published manuscript
  • study design

The Cochrane Handbook states that inclusion criteria should be broad enough to capture all the relevant variety of publications in which the intervention has been used but narrow enough "to ensure that a meaningful answer can be obtained when studies are considered together"

Protocol Resources

After you write the protocol, you should register it with a review registry. There are numerous review registries available, such as PROSPERO or OSF. Registration is free and open to anyone undertaking systematic reviews. Some journals also publish systematic review protocols.

 

NOTE: Scoping reviews may not be registered with PROSPERO.  Currently, they can be registered with the Open Science Framework (OSF) or Figshare. 

 

OSF can be used to pre-register a systematic or scoping review protocol and to share documents such as a citation management library, search strategies, and data extraction forms. Unlike other registries, evidence synthesis author teams do not submit their protocols for review by an editorial board before they are accepted and pre-registered on OSF. Instead, create your own pre-registration.

Protocols may be eligible for publication in certain journals in certain disciplines. Here are a few examples.

 

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