Feasibility of implementing a comprehensive warfarin pharmacogenetics service

Study objective: To determine the procedural feasibility of a pharmacist-led interdisciplinary service for providing genotype-guided warfarin dosing for hospitalized patients newly starting warfarin.

Design: Prospective observational study.

Setting: A 438-bed tertiary care hospital affiliated with a large academic institution.

Patients: Eighty patients who started warfarin therapy and were managed by a newly implemented pharmacogenetics service.

Intervention: All patients received routine warfarin genotyping and clinical pharmacogenetics consultation.

Measurements and main results: The primary outcomes were percentage of genotype-guided dose recommendations available prior to the second warfarin dose and adherence of the medical staff to doses recommended by the pharmacogenetics service. Of 436 genotype orders placed during the first 6 months of the service, 190 (44%) were deemed appropriate. For the 80 patients on the service who consented to data collection, 76% of the genotypes were available prior to the second warfarin dose. The median (range) time from genotype order to genotype result was 26 hours (7-80 hrs), and the time to genotype-guided dose recommendation was 30 hours (7-80 hrs). A total of 73% of warfarin doses ordered by the medical staff were within 0.5 mg of the daily dose recommended by the pharmacogenetics consult service.

Conclusion: Providing routine genotype-guided warfarin dosing supported by a pharmacogenetics consult service is feasible from a procedural standpoint, with most genotypes available prior to the second warfarin dose and good adherence to genotype-guided dose recommendations by the medical staff.