CRD Summary: This review concluded that the routine use of pharmacogenomic testing for the initiation of warfarin therapy was not supported by the evidence. Given the lack of reporting of the review process and quality assessment, the small number of participants and the likelihood that the review did not include the entire evidence base, the reliability of the conclusions are uncertain.

CRD Commentary: The authors addressed a clear review question, but had poorly defined inclusion criteria. The search for studies was limited and restricted to studies published in English. The review process was poorly reported, and it was unclear whether methods were used to reduce error and bias. The authors did not assess the quality of the included studies. The number of participants included in the review was extremely small. The decision to combine studies in a narrative seemed appropriate. Given these limitations, the reliability of the results of the included studies and the proportion of available evidence that was identified and included in the review are uncertain, therefore, the reliability of the conclusions are uncertain.