Genotype-Guided Warfarin Dosing in Patients With Mechanical Valves: A Randomized Controlled Trial.

Background: The clinical utility of genotype-guided warfarin dosing remains controversial. The objective of this trial was to evaluate the efficacy and safety of genotype-guided warfarin dosing in East Asians.

Methods: A double-blind, randomized control trial was performed to compare a genotype-guided dosing algorithm (CYP2C9, VKORC1, and CYP4F2) with a clinical-guided one in the initiation treatment for patients with mechanical heart valves. The primary outcomes included the time to reach a stable dose and the percentage of time in the therapeutic range (TTR).

Results: Two hundred one patients were randomly assigned to treatment, 101 to control and 100 to study. The major bleeding and thromboembolic event-free rate in the study group was 97.0% (95% confidence interval: 90.9% to 99.2%). Compared with the control group, the study group shortened the time to reach a stable dose (mean: 42.09 ± 23.655 days versus 33.52 ± 20.044 days, p = 0.009). The TTRs were 47.257% and 47.461% in the control and study group (p = 0.941), respectively. Patients with the CYP2C9 *1/*3 genotype had higher international normalized ratio (INR) variability than patients with the CYP2C9 *1/*1 genotype (p = 0.024). Compared with normal and sensitive responders, the highly sensitive responders were at increased risk of an INR of 4.0 or greater (p < 0.05).

Conclusions: The genotype-guided warfarin dosing was safe and might be more efficient for the time to reach a stable dose. Pharmacogenomic testing might be beneficial to identify the patients with the CYP2C9 *1/*3 genotype and the highly sensitive responders, who were in the high-risk subgroup of patients with mechanical heart valves. An appropriately powered study is needed to further confirm these findings.