Background: Despite the recent emergence of new oral anticoagulants, vitamin K antagonists remain the primary therapy in patients with atrial fibrillation and the only therapy licensed for use in patients with artificial heart valves.
Objective: The aim of this study was (a) to assess the impact of clinical and genetic factors on acenocoumarol (AC) dose requirements and the percentage of time in therapeutic range (%TTR) and (b) to develop pharmacogenetic-guided AC dose calculation algorithm.
Materials and methods: We included 235 outpatients of the Institute of Cardiology (Warsaw), mean age 69.3, 46.9% women, receiving AC for artificial heart valves and/or atrial fibrillation. A multiple linear-regression analysis was performed using log-transformed effective AC dose as the dependent variable, and combining CYP2C9 and VKORC1 genotyping with other clinical factors as independent predictors.
Results: We identified factors that influenced the AC dose: CYP2C9 polymorphisms (P=0.004), VKORC1 polymorphisms (P<0.0001), age (P<0.0001), creatinine clearance lower than 40 ml/min (P=0.035), body mass (P=0.02), and dietary vitamin K intake (P=0.026). Clinical and genetic factors explained 49.0% of AC dose variability. We developed a dosing calculation algorithm that is, to the best of our knowledge, the first one to assess the effect of such clinical factors as creatinine clearance and dietary vitamin K intake on the AC dose. The clinical usefulness of the algorithm was assessed on separate validation group (n=50) with 70% accuracy. Dietary vitamin K intake higher than 200 mcg/day improved international normalized ratio control (%TTR 73.3±17 vs. 67.7±18, respectively, P=0.04).
Conclusion: Inclusion of a variety of genetic and clinical factors in the dosing calculation algorithm allows for precise AC dose estimation in most patients and thus improves the efficacy and safety of the therapy.