Economic evaluation of an HIV prevention intervention for seropositive injection drug users

Objective To assess the cost-effectiveness of Intervention for HIV-Seropositive injection drug users-Research and Evaluation (INSPIRE), designed to reduce risky sexual and needle-sharing behaviors in research sites in four US cities (2001-2003). Methods We collected data on program and participant costs. We used a mathematical model to estimate the number of sex partners of injection drug users expected to become infected with human immunodeficiency virus (HIV) (with and without intervention), cost of treatment for sex partners who became infected, and the effect of infection on partners' quality-adjusted life expectancy. We determined the minimum effect that INSPIRE must have on condom use among participants for the intervention to be cost-saving (intervention cost less than savings from averted HIV infections) or cost-effective (net cost per quality-adjusted life year saved less than $50,000). Results The intervention cost was $870 per participant. It would be cost-saving if it led to 53 percent reduction in the proportion of participants who had any unprotected sex in 1 year and cost-effective with 17 percent reduction. If behavior change lasted 3 months, the cost-effectiveness threshold was 66 percent; if 3 years, the threshold was 6 percent. Conclusions Although cost-saving thresholds may not be achievable by the intervention, we anticipate that cost-effectiveness thresholds will be attained.