CRD summary: This review examined the efficacy of vitamin K in treating excessive anticoagulation. The authors concluded that the limited evidence available suggests that oral or intravenous, but not subcutaneous, vitamin K are more effective than withholding anticoagulation therapy. The methods employed to combine the studies were inappropriate, thus it is impossible to determine whether these conclusions are reliable.

CRD commentary: The review question and the inclusion criteria were specific and clear. The authors searched a number of relevant sources but did not appear to search for unpublished studies, which might have introduced publication bias into the review. The potential for language bias was appropriately addressed. The authors used appropriate methods to minimise bias and error in the study selection, validity assessment and data extraction processes. However, although the authors stated that data on patient characteristics were extracted, these were not reported in the paper. The use of the Jadad scale to assess the validity of non-randomised trials as well as RCTs is unlikely to provide an adequate assessment of their quality. The decision to use the trial arm, rather than the randomised trial, as the unit for analysis was inappropriate as this method discards the benefits of a randomised comparison. Consequently, it is not possible to determine if the authors' conclusions accurately reflect the evidence contained in the review, or whether they are reliable.