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Systematic Reviews: Protocols

Collaborative support for researchers undertaking systematic reviews

What is a protocol?

Like any well-designed research study, a systematic review/evidence synthesis should begin with the development of a protocol. A protocol is a detailed description of the rationale, objectives, and methods of the review. Systematic review standards, best practices, and guidelines, such as PRISMAThe Cochrane Handbook, and The National Academies of Sciences (previously Institute of Medicine) all require or recommend registering a protocol before performing a systematic review. Some journals require a systematic review have a registered protocol in order to be accepted for publication. 

"The preparation of a protocol is an essential component of the systematic review process; it ensures that a systematic review is carefully planned and that what is planned is explicitly documented before the review starts, thus promoting consistent conduct by the review team, accountability, research integrity, and transparency of the eventual completed review.

When clearly reported protocols are made available, they enable readers to identify deviations from planned methods in completed reviews and whether they bias the interpretation of a review results and conclusions."

Moher D, Shamseer L, Clarke M, Ghersi D, Liberati A, Petticrew M, Shekelle P, Stewart LA. Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) 2015 statement. Syst Rev. 2015;4(1):1. doi: 10.1186/2046-4053-4-1

What information should I put in my protocol?

PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) has a checklist for just protocols (PRISMA-P). Your protocol should outline administrative information, rationale and objective, and planned methods for your review.  

If registering your protocol with a particular outlet (e.g., PROSPERO) your protocol should adhere to their specific registration template.


Your protocol should not be generic text - rather, it should be specific to your review question. At minimum, a protocol should provide explicit information on:

  • Funding sources or COI
  • Review question & background
  • PICO
  • Inclusion/exclusion criteria
  • Searches
  • Study selection
  • Data extraction
  • Risk of bias assessment
  • Strategy for data synthesis

What should I do with my protocol?

Your completed protocol should be made publicly available/registered as early in the process as possible. Best practice recommends registering a protocol before the team begins screening results. PROSPERO will not accept a protocol if data extraction has begun. 

There are several outlets for making a protocol publicly available, although not all outlets are appropriate for all reviews. Minimum requirements for a protocol to be considered "registered" are that it is freely and publicly available, accessible via a stable and unique URL, and publicly provides history of edits or versioning. The URL must then be made available in the review's final manuscript.

Pieper, D., Rombey, T. Where to prospectively register a systematic review. Syst Rev 11, 8 (2022).