Evaluation of commercial platforms for rapid genotyping of polymorphisms affecting therapeutic warfarin dose

Excerpt

Background Initiation of oral anticoagulation therapy with warfarin is challenging due to the risk of bleeding and thrombotic complications. A third of warfarin dosing variability is accounted for by patients’ genotypes for three single nucleotide polymorphisms (SNPs), two in the cytochrome P450 2C9 gene that reduce warfarin metabolism (*2 and *3) and one in the promoter region of the Vitamin K reductase complex 1 (VKORC1) gene that increases warfarin sensitivity. Accurate and rapid SNP determination is required to use pharmacogenetic warfarin dosing algorithms to improve initial anticoagulation treatment. Methods We compared the accuracy of three commercial genotyping systems. 112 coded DNA samples were genotyped for CYP 2C9 *2, *3, and VKORC1 3673SNP status on: (1) INFINITI^® analyzer (Autogenomics, Carlsbad, CA), (2) Invader^® assay (Third Wave Technologies, Madison WI) and TECAN GENios FL fluorescence plate reader (Zurich, Switzerland) and (3) Tag-It^® Mutation Detection assay (Tm Bioscience, Toronto, Canada) and Luminex^® 200 xMAP instrument (Austin, TX). Results were compared to a reference genotype-by-sequencing method: Pyrosequencing^® (Uppsala, Sweden). Technologists performing the tests were blinded to the results from each instrument. Discordant results were resolved by directional sequencing performed by a different laboratory. Results Conclusion The three commercial platforms were 100% accurate for *2 and *3 SNP genotyping. VKORC1 3673 SNP genotyping is technically more challenging, rarely producing incorrect results. …