Lack of association of clinical factors (SAMe-TT2R2) with CYP2C9/VKORC1 genotype and anticoagulation control quality

Background and Purpose Advantages of new oral anticoagulations may be greater in atrial fibrillation (AF) patients of poor anticoagulation control with warfarin. The SAMe-TT₂R₂ scoring system, based on clinical variables, was recently developed to aid in identifying these patients. In this study, we investigated the association of this clinical composite score with genetic factors related warfarin dosing and the quality of anticoagulation control. Methods Clinical and genetic data were collected from 380 consecutive Korean patients with AF (CHA₂DS₂-VASc score, 3.5±1.8) who were followed for an average of 4 years. We evaluated factors associated with time in therapeutic range (TTR, INR 2-3), including the CYP2C9 and VKORC1 genotypes and the SAMe-TT₂R₂ score (Sex female, Age <60 years, Medical history [>two co-morbidities], Treatment [interacting drugs, e.g., amiodarone], To­bacco use within 2 years [doubled], and Race non-white [doubled]). Results The average SAMe-TT₂R₂ score was 3.4±0.9, range 2-7; and 153 patients (40.2%) had SAMe-TT₂R₂ scores ≥4. Time in specific INR ranges varied depending on the VKORC1 genotype but not with the CYP2C9 genotype or the SAMe-TT₂R₂ score. TTR was higher in patients with the VKORC1 1173C>T than in VKORC1 TT (61.7±16% vs. 56.7±17.4%, P=0.031). Multivariate testing showed that VKORC1 genotype but not the SAMe-TT₂R₂ score was significantly associated with labile INRs. There was no correlation between the SAMe-TT₂R₂ scores and pharmacogenetic data. Conclusions A genetic factor, but none of the common clinical and demographic factors, as combined in the SAMe-TT₂R₂ score, was associated with the quality of anticoagulation con­trol in Korean patients with AF.