Warfarin genotyping using three different platforms.

Genetic testing for common variants in the CYP2C9 and VKORC1 genes may provide useful clinical information to guide dosing patients receiving oral warfarin. Specifically, the CYP2C9*2, CYP2C9*3 and either the VKORC1-1639 G>A or VKORC1 1173C>T polymorphisms can be used to help predict an approximate warfarin maintenance dose needed for a particular patient. Although clinical uptake and use of this genotyping has been slow, an increasing body of literature provides evidence of the clinical utility of supplementing traditional warfarin dosing algorithms with a pharmacogenetic approach. The availability of multiple methods for clinical genotyping provides the opportunity for molecular diagnostic laboratories to introduce genotyping assays tailored to their specific needs based on variables such as testing volumes, staffing, available instrumentation and needed turnaround times. Three assays (Invader, Verigene and TaqMan) designed to detect three genetic variations associated with warfarin dosing are evaluated and compared as potential clinical tests to assist in patient care. Identical genotypes were reported by each assay for all samples tested but the assays were found to differ in turnaround time, approval status by the U.S. Food and Drug Administration (FDA), requirements for amount of input genomic DNA and other logistical factors that might make each assay more favorable in different settings.