Summary
Variant cytochrome P450 (CYP) 2C9 genotypes are associated with low maintenance dose
requirement of warfarin therapy and increased risk of major bleeding events. The objective
of the present study was to evaluate the potential clinical and economic outcomes
of using CYP2C9 genotype data to guide the management of anticoagulation therapy and
to identify influential factors affecting the cost-effectiveness of this treatment
scheme. A decision tree was designed to simulate, over 12 months, the clinical and
economic outcomes of patients newly started on warfarin associated with two alternatives:
(1) no genotyping (non-genotyped group) and (2) CYP2C9 genotyping prior to initiation
of warfarin therapy (genotyped group). Nongenotyped group patients would receive standard
care of an anticoagulation clinic (AC). In the genotyped group, patients with at least
one variant CYP2C9 allele would receive intensified anticoagulation service. Most
of the clinical probabilities were derived from literature. The direct medical costs
were estimated from the Diagnosis-Related Group charges and from literature. The total
number of events and the direct medical cost per 100 patient-years in the genotyped
and non-genotyped groups were 9.58 and USD155,700, and, 10.48 and USD 150,500, respectively.
The marginal cost per additional major bleeding averted in the genotyped group was
USD 5,778. The model was sensitive to the variation of the cost and reduction of bleeding
rate in the intensified anticoagulation service. In conclusion, the pharmacogenetics-oriented
management of warfarin therapy is potentially more effective in preventing bleeding
with a marginal cost. The cost-effectiveness of this treatment scheme depends on the
relative cost and effectiveness of a pharmacogenetics-oriented intensified anticoagulation
service comparing to the standard AC care.
Keywords
Warfarin - CYP2C9 - cost-effectiveness
