CPT® Code 81355

VKORC1 (vitamin K epoxide reductase complex, subunit 1) (eg, warfarin metabolism), gene analysis, common variant(s) (eg, -1639G>A, c.173+1000C>T)

The CPT® Code 81355 pertains to the molecular genetic testing of the VKORC1 gene, which is crucial for understanding an individual's response to warfarin, a commonly used anticoagulant. This gene encodes the vitamin K epoxide reductase complex, subunit 1, an enzyme that plays a vital role in the vitamin K cycle, which is essential for blood clotting. The testing specifically identifies common variants of the VKORC1 gene, such as -1639G>A and c.173+1000C>T. The variant -1639G>A is a single nucleotide polymorphism (SNP) located in the promoter region of the VKORC1 gene. This mutation can lead to a reduction in the functional copies of the VKORC1 protein, thereby limiting the enzyme's availability for the conversion of vitamin K 2,3-epoxide to its active form. Understanding these genetic variations is particularly important for patients undergoing long-term warfarin therapy, as they can significantly influence the metabolism of the drug. For instance, individuals with the -1639G>A variant may require lower doses of warfarin due to a slower metabolism and a longer half-life of the drug in their system. The presence of this mutation is notably prevalent in certain populations, with up to 90% of individuals in Asian populations and around 50% in Caucasian populations carrying the variant. Therefore, molecular genetic testing for VKORC1 is essential for tailoring warfarin dosing to ensure effective anticoagulation while minimizing the risk of adverse effects.