Economic evaluation of drug resistance genotyping for the adaptation of treatment in HIV-infected patients in the VIRADAPT study.

Background: Costs of antiretroviral therapy for HIV-infected patients have increased at a time when most countries are attempting to contain health care costs. Part of this increase results from HIV drug resistance associated with virologic failure and a subsequent shift to more complex and costly therapies. Genotypic guided treatment is associated with better virologic outcome. However, it is not yet known whether it will be cost effective. Methods: We present here an economic evaluation based on the results from the VIRADAPT study, a prospective, open-label, randomized trial comparing patients assigned to standard of care (n = 43), versus genotypic guided treatment (n = 64) for 6 months. Total follow-up for the extended trial was I year. Costs were computed from the viewpoint of the health care system. Hospitalization data were retrieved from the VIRADAPT study case report forms, costs were estimated from the cost of the corresponding diagnosis-related groups derived from the French national cost data base: these were actual costs and not charges. Data on the volume of tests prescribed, drugs, and clinic visits were retrieved from the VIRADAPT study database. The unit costs of tests and clinic visits were determined using the French national Social Security reimbursement price; costing of drugs used were based upon purchase price by either retail pharmacies or hospitals. Genotyping using TruGene HIV-1 assay was estimated at $500 per test from manufacturer's data (all figures in this paper are expressed in U.S. dollars). Results: Total mean (standard deviation) yearly costs per patients were $20,412 (±$10,129) in the standard of care group and $18,484 (±$9,652) in the genotyping group (p = .35). Drug costs represented 55% of total costs. There was a trend toward a decrease in drug costs in the genotyping arm (p = .07), the greatest reduction being in the decreased use of protease inhibitors in the genotyping arm. The additional expense of genotyping appeared to be offset by the savings obtained in drug costs. Conclusion: In our study, the cost of drug resistance testing is offset by a reduced use of protease inhibitors and their attendant costs. Although not reaching statistical significance, this trend in the reduction of drug costs and drug use presents a great interest for future trials.