Perspective:

This study attempted to determine if more patient-specific information in the form of genetic testing leads to better clinical warfarin dosing. Prior small clinical trials have suggested this is not the case, as the standard approach to dose adjustment based on INR testing resulted in similar therapeutic efficacy. These studies may have been underpowered, however. The current study suggests that the pharmacogenetic algorithms tested resulted in statistically fewer out of range of INR test results, and more TTR, at 1 and 3 months. Several questions remain, however. First, is it feasible to use genetic testing in routine dosing of warfarin and existing clinical care settings, without incurring unreasonable expense? (Or for that matter, is it feasible to use an algorithm that algebraically computes 19 potential factors to determine dose?) Second, are the differences in TTR and number of out of range INR test results seen in this study clinically relevant? That is, is there any difference in bleeding or thrombotic outcomes? For the time being, it remains unclear how and when pharmacogenetic testing should be incorporated into the routine clinical care of patients receiving warfarin. The results of four large randomized trials currently underway may provide greater clarity.