Allelic Variants in the Warfarin-related Genes VKORC1 and CYP2C9 in a Western Saudi Population

To investigate the allele and genotype frequencies of the warfarin-related genes VKORC1 (-1639G>A), CYP2C9*2, and CYP2C9*3 among healthy Saudis. This cross-sectional study involved 125 unrelated healthy Saudis ages 18–60 years visiting the King Abdulaziz University Hospital (KAUH) in Jeddah, Western Saudi Arabia. The Oragene™ DNA saliva collection kits were used to collect and extract DNA from saliva samples. A polymerase chain reaction-restriction fragment length polymorphism analysis was used to detect the mutant alleles. Over 51.4% of the Saudi participants carried one or more mutant alleles. The frequency of the VKORC1 (-1639G>A) allele in Saudi was relatively high at 54.8%. The frequencies of the CYP2C9 allele were 19.6% and 54% for the CYP2C9*2 and CYP2C9*3 alleles, respectively, which are substantially more abundant than in other populations. The observed high frequencies of VKORC1 (-1639G>A) and CYP2C9*2 and CYP2C9*3 polymorphisms suggest that genetic testing should be considered before initiating warfarin therapy to predict the optimal initial dose of warfarin and minimize warfarin-related side effects.