Pharmacogenetics of warfarin and healthcare costs – Real‐world data analysis

PURPOSE: Variants in CYP2C9 and VKORC1 genes have been associated with individuals' sensitivity to warfarin. The aim of this study was to investigate the differences of healthcare costs of genetically normal and genetically sensitive warfarin responder groups. METHODS: This was a retrospective study linking genotype data from three Finnish biobanks (THL Biobank, Auria Biobank, Helsinki Biobank) with healthcare encounter data of the Finnish Institute of Health and Welfare (THL), drug dispensation data from the Social Insurance Institution of Finland (Kela) and laboratory data from Finnish hospital districts and municipalities. We compared the normal and sensitive warfarin responder groups in terms of healthcare costs related to bleeding and thromboembolic events, INR tests and medication purchases. RESULTS: We found a trend towards increased bleeding-related hospital costs in the sensitive warfarin responder group (881 patients) when compared with the normal responders (1627 patients) with a per patient difference of 150.9 €/year (95% CI: -55.1, 414.6 €/year, p = 0.087). INR test costs were higher in the sensitive responder group with a difference of 7.2 €/year (95% CI: -1.5, 16.4 €/year, p = 0.047). Medication costs were significantly lower in the sensitive responder group with a difference of -14.4 €/year (95% CI: -15.8, -12.9 €/year, p < 0.001). CONCLUSIONS: The difference in the costs of bleeding-related hospitalization between genetically sensitive and normal warfarin responders may justify genotype-guided warfarin dosing. Further studies with larger sample sizes would be needed to verify the result.