Methodology for reviewing as review article

Use two independent reviewers (COSMIN methodology for assessing the content validity of PROMs, User manual version 1.0, p.10)

The review team will need to make judgements when rating the content validity. We therefore recommend that all ratings are done by two reviewers, independently. This is good practice for all kind of systematic review. ... All ratings should be compared and consensus reached among the reviewers, if needed, with help of a third reviewer.

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