A protocol is a written plan of work for an evidence synthesis project.  Systematic reviews that are properly completed MUST have a protocol in order to ensure reproducibility. Other types of ES projects, such as scoping review and meta-analyses have specific guidelines for reporting that outline the use of a protocol as well. Further reporting guidelines are in development. Not all types of evidence synthesis methodologies have written guidelines for creating a protocol. However, a good written protocol improves the quality of an evidence synthesis project, regardless of methodology chosen.

Protocols enable replication, make the process transparent for readers who are making decisions based upon the findings, and allow readers to verify results or evaluate a project for risk of bias. It also organizes and clarifies the intent of the project between collaborators, thereby improving inter-rater reliability and leading to higher quality outcomes. Many journals require a published protocol to accept systematic review articles for publication.

Protocols are made public in order to ensure that the project adheres to the process created by the research group. The protocols can be added to registries, online portals that make a large number of protocol documents available to the research community or repositories, online servers that hold files organized by project.

Parts of a good quality protocol generally should include:

• rationale for the review
• a well developed research question that is structured according to a framework such as PICO or SPICE
• inclusion and exclusion criteria
• a set of articles that should be included in the final search set (exemplar articles)
• a rigorously designed search string for at least one database
• a list of all databases and resources that will be searched
• a plan for the management of citations and for assessment of the citations resulting from the search string
• If appropriate for the evidence synthesis methodology, as assessment of the methodologies used in the article or a risk of bias assessment for individual studies
• a description of the project plan for synthesizing the resulting data

Different types of evidence synthesis projects have different requirements for what be included in the protocol. Professional organizations in the health sciences have created a number of protocol templates. The most frequently used are listed below.

Review registries are online databases of reviews. They allow researchers to avoid duplication of projects. They allow transparency, support open science, and reduce reporting bias. (PROSPERO, 2025) These registries can be specific to a research discipline or project methodology (e.g. PROSPERO for health related outcomes systematic reviews protocols). These registries include peer review of the protocol before acceptance and registration. 

Not all disciplines have dedicated protocol registries. In those cases, there are several options for researchers.

• Open Science Framework - Online repository where a protocol for any discipline can be housed. Does not have peer review of protocols, but does allow registration of the protocol.
• Figshare - Online repository where a protocol for any discipline can be housed. Does not have peer review of protocols, but does allow registration of the protocol.

Some journals and services will also register protocols.

Biomed Central

BMJ Open

Systematic Reviews, a BioMed Central Journal

JBI Evidence Synthesis