Genetic and nongenetic factors associated with warfarin doserequirements in Egyptian patients

Background and objective: Warfarin is a commonly used oral anticoagulant with a narrow therapeutic index and various genetic and clinical factors that influence interpatient variability in dose requirements. This study investigated the impact of genetic and nongenetic factors on warfarin dose requirements in Egyptians. Methods: DNA was extracted from 207 patients taking warfarin for more than 2 months and genotyped for VKORC1 (3673 G>A), CYP2C9 *2*3*4*5*8, CYP4F2 (V33M; rs2108622), APOE (rs429358, rs7412), and CALU(rs339097) gene polymorphisms. Linear regression modeling was conducted to identify the genetic and nongenetic factors that independently influence warfarin dose requirements. RESULTS: VKORC1 3673 AA or GA genotype (P<0.0001), one or two variant alleles of CYP2C9 gene (P=0.0004), APOE ε2 haplotype (P=0.01), and increasing age (P<0.0001) were all associated with lower warfarin dose, whereas smoking (P=0.025) and pulmonary embolism (P=0.0059) showed association with higher warfarin doses. These factors explained 31% of the warfarin dose variability. This is the first independent confirmation of the association of the CALU rs339097 variant with higher warfarin dose requirement, although inclusion of thissinglenucleotide polymorphism in the multiple regressionmodel failed to achieve significance (P=0.066). CYP4F2 (V33M) polymorphism was not significant (P=0.314), despite itshigh frequency in the studied population (42%). Conclusion: The study shows that VKORC1, CYP2C9 polymorphisms, APOE ε2 variant, and several clinical/demographic variables are important determinants of warfarin dose requirements in Egyptian patients. The percentage of variability explained by these factors is lowerthan in those of European ancestry, but similar tothevariability explained in Asians and African ancestry. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.