A systematic review starts with a clearly defined question and uses systematic and explicit methods to identify, select and critically appraise relevant research. When writing your question, it is important to state the objectives and decide on eligibility criteria for included studies.
The protocol spells out the rationale and methods for a systematic review. It acts as a guide for searches and provides details like the population of interest, study size, location, date range, outcomes etc. It's purpose is to help ensure that results aren't arbitrary.
Registering a study protocol
It is best practice to register your protocol at the outset. This helps avoid duplication and allows others to see your review methods. There are a number of places a review can be registered:
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