A protocol is a plan, a document or set of steps to be followed in a study. A protocol for a systematic review should describe:
The publication of a protocol for a review prior to knowledge of the available studies reduces the impact of review authors’ biases, promotes transparency of methods and processes, reduces the potential for duplication and allows peer review of the planned methods.
Preferably, a protocol should also be registered. This is actually one of the items for reporting in the PRISMA Guidelines. Some journals – for instance BMJ, The Lancet and British Journal of Dermatology – requires a registered protocol for systematic reviews. There are several reasons for this. For instance, it increases the overall transparency of the review, making it more scientifically sound. Additionally, the registration of the protocol also adds visibility to your review. This can help to avoid duplication of the work.
There is also a guideline for developing protocols för systematic reviews: PRISMA-P (which aims to facilitate the development and reporting of systematic review protocols) and a specific database aimed for the registration of protocols for systematic reviews: PROSPERO – International Prospective Register of Systematic Reviews.
Karolinska Institutet University Library (2022). Systematic reviews [Structure & Documentation] : https://kib.ki.se/en/search-evaluate/systematic-reviews,
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Moher, D., Shamseer, L., Clarke, M., Ghersi, D., Liberati, A., & Petticrew, M. et al. (2015). Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement. Systematic Reviews, 4(1). doi: 10.1186/2046-4053-4-1
PROSPERO is an international database of prospectively registered systematic reviews in health and social care, welfare, public health, education, crime, justice, and international development, where there is a health related outcome. Key features from the review protocol are recorded and maintained as a permanent record. PROSPERO aims to provide a comprehensive listing of systematic reviews registered at inception to help avoid duplication and reduce opportunity for reporting bias by enabling comparison of the completed review with what was planned in the protocol.
Systematic reviewers are supposed to register with PROSPERO at the inception of their project by reporting their study protocol. Searching PROSPERO can reduce duplication when researchers locate a systematic review in process that is attempting to answer the same question they are. Reviewing protocols for systematic reviews written by others can help researchers develop their own protocols.
Jewell, S. (2017). Assembling the pieces of a systematic review - a guide for librarians. Rowman & Littlefield.