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Systematic review guide

A step by step guide to doing a systematic review

Prospective review protocols

A protocol should be prepared before a full review is started and then used as your roadmap in carrying out the review. It describes the rationale, hypothesis, and planned methods of the systematic review. Planning and specifying all your methods in advance reduces the risk of introducing bias into the review.
Protocols for reviews intended for publication should be registered on PROSPERO or another appropriate registry and updated as necessary.

Writing the protocol

To write a prospective protocol you will need to be able to answer these questions in detail:

  • What is already known on the research area and what will your review add? 
  • Why does it matter for the population being studied? 
  • What is the review aiming to achieve? 
  • What precise question is being answered? 
  • What your search strategy will be and which databases and grey literature sources you will use (including a fully realised systematic search strategy for one database - usually MEDLINE)
  • How will you conduct study selection, data extraction and quality assessment? 
  • What method of synthesis will you use? Can you perform a meta-analysis or will a narrative synthesis be suitable?
  • How will the review findings be disseminated? 
  • Who is conducting the review? 
  • What is the project timeline? 
  • If you have the appropriate resources in terms of time, people and experience?

Registering a protocol

Protocol registration creates a publicly accessible, permanent record of key information about how your review is designed.
Registration of your protocol will not lock you into a rigid plan, it’s about being clear, open and purposeful in your research. If some elements of your review need adjustment (as they often do in research), you can update any information in the preregistration template. The key is to record any deviations from your original plan and to and explain why they were necessary.
Regisration aid research transparency with benefits including:

  • Reducing bias: a protocol creates a frame of reference for you and other stakeholders to refer back to throughout the review process. Once registered, any deviations you do need to make in the review are able to be tracked and visible in the protocol’s audit trail.  
  • Reducing duplication: other researchers will be aware of your review and will not waste their time answering the same question. 
  • Publication and peer review: a registered protocol can be seen as a mark of quality by peer reviewers/journal editors as the protocol will show how much the final review deviated from its pre-defined criteria. 

Where to register

Protocols with at least one specific human health related outcome, or with a methodology review with a clear link to human health, should be registered on PROSPERO using their guidance notes and template. PROSPERO free of charge and is funded by the National Institute for Health Research (NIHR). UK-based registrations are processed on a priority basis.
Exceptions for PROPERO registration are: 

  • Reviews with no human health related outcomes
  • Scoping, mapping and literature reviews - see the Joanna Briggs Institute’s (JBI) guidance for the development of a scoping review protocol
  • Cochrane Reviews - they are uploaded automatically to PROSPERO 
  • Completed reviews
  • Reviews that will not be published - mini or partial reviews for coursework or for any other project that is less than a full systematic review

Students and others learning how to do a review or register a review may use the PROPSERO "Student Project" option when registering. This lets them use PROSPERO and share their records with supervisors. However, the protocol and records will not be published in PROSPERO and will not appear in PROSPERO searches.

 

Other registers

This blog post from Cochrane details some of the features of other protocol registers and includes information about any potential fees charged.