Subjects who are randomized to 90 days of follow-up and whose warfarin dose was determined using the genetic information from the GenoSTAT test and clinical information through the warfarindosing.org website

Subjects who are randomized to 90 days of follow-up and whose warfarin dose was determined using the genetic information from clinical information alone through the warfarindosing.org website

Subjects who are followed 30 days of follow-up and whose warfarin dose was determined using the genetic information from the GenoSTAT test and clinical information through the warfarindosing.org website

Use of genetic information from the GenoSTAT test to determine the warfarin dose

To determine if using warfarin-related pharmacogenetic information in calculating warfarin doses will change the incidence of warfarin-related clinical events, including major hemorrhage and thromboembolic events, at 30 days after initial dose, when compared to warfarin doses calculated without pharmacogenetic data.

Comparison of the number of INR tests performed before warfarin dose stabilization (i.e. two consecutive INR tests within the target range)

Comparison of the cumulative warfarin dose necessary to reach warfarin dose stabilization (i.e. two consecutive INR tests within the target range)