A PCR method for VKORC1 G-1639A and CYP2C9 A1075C genotyping useful to warfarin therapy among Japanese

Warfarin is widely prescribed for patients with the risk of thromboembolism around the world. The inter-individual and inter-racial differences in appropriate dosage depend highly on age, body weight, and genetic factors. A lot of studies including genome-wide association studies revealed that vitamin K epoxide reductase complex, subunit 1 (VKORC1) G-1639A and Cytochrome P450 (CYP) 2C9 A1075C are the most strong genetic factors for determining warfarin effects in Asians and Africans. Since we developed a quick and inexpensive genotyping method, polymerase chain reaction with confronting two-pair primers (PCR-CTPP), the method was applied for these genotypes to examine the possibility to clinical use. Subjects were 436 examinees (117 males and 319 females, aged 32 to 85 years) who attended a health checkup program in Japan. The PCR-CTPP for VKORC1 G-1639A and CYP2C9 A1075C was conducted for the subjects, as well as the samples genotyped by DigiTag2 method. The allele frequencies of VKORC1 G-1639A were 0.085 for G and 0.915 for A, and those of CYP2C9 A1075C were 0.979 for A and 0.021 for C, being in Hardy-Weinberg equilibrium (p = 0.658 and p = 0.514, respectively). These frequencies were similar to those reported in the HapMap project. Genotyping for both SNPs by PCR-CTPP was replicated by DigiTag2 method. Our results indicated that the PCR-CTPP could be one of the alternative methods for genotyping VKORC1 G-1639A and CYP2C9 A1075C for Asians and Africans with similar allele frequencies to Japanese.