Use of genotypic resistance testing to guide hiv therapy: clinical impact and cost-effectiveness.

BACKGROUND Genotypic sequencing for drug-resistant strains of HIV can guide the choice of antiretroviral therapy. OBJECTIVE To assess the cost-effectiveness of genotypic resistance testing for patients acquiring drug resistance through failed treatment (secondary resistance) and those infected with resistant virus (primary resistance). DESIGN Cost-effectiveness analysis with an HIV simulation model incorporating CD4 cell count and HIV RNA level as predictors of disease progression. DATA SOURCES Published randomized trials and data from the Multicenter AIDS Cohort Study, the national AIDS Cost and Services Utilization Survey, the Red Book, and an institutional cost-accounting system. TARGET POPULATION HIV-infected patients in the United States with baseline CD4 counts of 0.250 x 10(9) cells/L. TIME HORIZON Lifetime. PERSPECTIVE Societal. INTERVENTIONS Genotypic resistance testing and clinical judgment, compared with clinical judgment alone, in two contexts: after initial treatment failure (secondary resistance testing) and before initiation of antiretroviral therapy (primary resistance testing). OUTCOME MEASURES Life expectancy, quality-adjusted life expectancy, and cost-effectiveness in dollars per quality-adjusted life-year (QALY) gained. RESULTS OF BASE-CASE ANALYSIS Secondary resistance testing increased life expectancy by 3 months, at a cost of $17 900 per QALY gained. The cost-effectiveness of primary resistance testing was $22 300 per QALY gained with a 20% prevalence of primary resistance but increased to $69 000 per QALY gained with 4% prevalence. RESULTS OF SENSITIVITY ANALYSIS The cost-effectiveness ratio for secondary resistance testing remained under $25 000 per QALY gained, even when effectiveness and cost of testing and antiretroviral therapy, quality-of-life weights, and discount rate were varied. CONCLUSIONS Genotypic antiretroviral resistance testing following antiretroviral failure is cost-effective. Primary resistance testing also seems to be reasonably cost-effective and will become more so as the prevalence of primary resistance increases.