13.1.4  The importance of a protocol for a Cochrane review that includes non-randomized studies

Chapter 2 (Section 2.1) establishes the importance of writing a protocol for a Cochrane review before carrying out the review. As the methodological choices made during a review of NRS are complex and may affect the review findings, a protocol is even more important for a review that includes NRS. The rationale for doing a review that includes NRS (see Section 13.1.2) should be documented in the protocol. The protocol should include much more detail than for a review of randomized trials, pre-specifying key methodological decisions about the methods to be used and the analyses that are planned. The protocol needs to specify details that are not relevant for randomized trials (e.g. the methods planned to identify potential confounding factors and to assess the susceptibility of primary studies to confounding), as well as providing more detail about standard steps in the review process that are more difficult when including NRS (e.g. specification of eligibility criteria and the search strategy for identifying eligible studies).


The NRSMG recognizes that it may not be possible to pre-specify all decisions about the methods used in a review. Nevertheless, review authors should aim to make all decisions about the methods for the review without reference to the findings of primary studies, and report methodological decisions that had to be made or modified after collecting data about the study findings.