A protocol is a written document that acts as an a priori plan for your evidence synthesis project. Beginning your project with a clear plan is important, even if the methods change along the way.
If your methods (e.g., search queries, inclusion/eligibility criteria) do change after you finish your protocol, you should document those changes in your final manuscript. For instance, completed Cochrane reviews often have a section titled 'Differences between protocol and review’.
Protocols generally contain sections for:
For systematic reviews, PRISMA provides guidance for preparing a protocol, as does the Joanna Briggs Institute's Manual for Evidence Synthesis.
For scoping reviews, section 11.2 in the JBI Manual outlines protocol development
Once you've written the protocol for your evidence synthesis, consider publishing or registering it. Making the protocol publicly available, through publication or registration, improves research transparency, and can help avoid unnecessary duplication of work around the same review question.
Many journals will publish a protocol for research, including systematic reviews. See the 'Information for Authors' or 'Submissions' sections of journal's websites to determine what kind of articles they publish.
McGill Library. (2022). Guides: Systematic Reviews, Scoping Reviews, and Other Knowledge Syntheses: Developing the protocol. Retrieved February 4, 2022, from https://libraryguides.mcgill.ca/knowledge-syntheses/protocol