Feasibility of Implementing a Comprehensive Warfarin Pharmacogenetics Service

Abstract

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 483-bed hospital affiliated with a large academic institution Participants Eighty patients started on warfarin and managed by a newly implemented pharmacogenetics service. Intervention Routine warfarin genotyping and clinical pharmacogenetics consultation Measurements and Main Results The primary outcomes were percent 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 during the first 6 months of the service, 190 were deemed appropriate. For 80 patients on the service who consented to data collection, 77% of genotypes were available prior to the second warfarin dose. The median (range) time from the genotype order to the genotype result was 26 (7 to 80) hours, and the time to genotype-guided dosing recommendation was 30 (7 to 80) hours. Seventy-three percent of warfarin doses ordered by the medical staff were within 0.5 mg of the dose recommended by the pharmacogenetics consult service. Conclusions Providing routine genotype-guided warfarin dosing supported by a pharmacogenetics consult service is feasible from a procedural standpoint, with the majority of genotypes available prior to the second warfarin dose and good adherence to genotype-guided dose recommendations by the medical staff.

Oral anticoagulation: a critique of recent advances and controversies

“…Furthermore, some health insurance and healthcare providers have refused to pay for genotyping before warfarin prescription [30]. This has made the uptake of genotyping haphazard, being implemented only in some specialist centers [31].…”

Iterative Development and Evaluation of a Pharmacogenomic-Guided Clinical Decision Support System for Warfarin Dosing

“…Prescribers in the validation phase more commonly ordered the dose recommended by the CDSS for both initiating and adjusting warfarin doses. The frequency of ordering the CDSS recommended dose was similar to another study which utilized warfarin pharmacogenomics to provide dosing recommendations [43].…”

“…Prescribers in the validation phase more commonly ordered the dose recommended by the CDSS for both initiating and adjusting warfarin doses. The frequency of ordering the CDSS recommended dose was similar to another study which utilized warfarin pharmacogenomics to provide dosing recommendations [43].There was one instance during the development iteration where a prescriber unknowingly ordered a dose of 12.5mg, a potentially fatal dose, but this did not occur during the validation iteration. It should be noted, however, that while a small number of participants can identify a large number of problems with an interface, rare events and 'critical usability incidents' , such as an accidental fatal warfarin dose, may require a greater number of participants.…”

“…While a routine genotype-guided warfarin dosing service has been shown to be feasible from a procedural standpoint, there has been limited incorporation into clinical practice [19,20]. An important setback is the fact that there are conflicting reports regarding the effectiveness of incorporating genetic testing into warfarin dosing [21,22].…”

“…Pharmacogenomic tests may help clinicians manage warfarin more effectively and minimize the risk of serious bleeding [16,17]. In August 2007, the United States FDA approved a change in warfarin labeling to incorporate information related to how CYP2C9 and VKORC1 genetic variability can impact appropriate warfarin dosing and response [18].While a routine genotype-guided warfarin dosing service has been shown to be feasible from a procedural standpoint, there has been limited incorporation into clinical practice [19,20]. An important setback is the fact that there are conflicting reports regarding the effectiveness of incorporating genetic testing into warfarin dosing [21,22].…”