PID6: HIV/AIDS HEALTH STATE UTILITIES USING COMMUNITY AND PATIENT PREFERENCE WEIGHTS: WHEN DOES IT MATTER?

Abstract

OBJECTIVES: To compare utilities for HIV/AIDS health states derived from community-based preferences with those derived from patients, and to examine the implications of differences for a cost-effectiveness analysis of early versus deferred treatment of HIV patients presenting with CD4 cell counts of 500/μL. METHODS: We used data from the HIV Cost and Services Utilization Study (HCSUS), a probability sample of 2,864 HIV-infected adults receiving care in the United States in 1996, to derive utilities for HIV/AIDS health states. Community-based utilities were calculated from the SF-6D responses in the HCSUS survey using algorithms derived by Brazier et al. Patient utilities were calculated from patient self-assessments using a rating scale transformation derived by Torrance et al. We used a computer-based state-transition simulation model of HIV disease to conduct cost-effectiveness analyses using both community and patient utilities. RESULTS: Patient utilities were significantly higher (by 4% to 9%, p < 0.001) than community utilities for all disease stages: for asymptomatic HIV patients 0.970 (0.963–0.977) vs. 0.937 (0.926–0.949); for symptomatic HIV patients 0.910 (0.902–0.919) vs. 0.841 (0.826–0.855); and for patients with a history of an AIDS-defining condition 0.845 (0.832–0.858) vs. 0.778 (0.761–0.795). The cost-effectiveness ratio of early therapy (initiated at 500 CD4 cells/μL) versus deferred therapy (initiated at <200 CD4 cells/μL) was $20,100/QALY using community utilities and $18,400/QALY using patient utilities. In a sensitivity analysis, when we assumed a 20% reduction in quality of life due to side effects during early therapy but not during deferred therapy, the cost-effectiveness ratio of early versus deferred therapy was $50,900/QALY using community utilities and $46,300/QALY using patient utilities. CONCLUSIONS: There are differences between community and patient utilities for HIV/AIDS health states. The impact of these differences on HIV/AIDS cost-effectiveness results should be considered when treatment side effects are important.