Methods. We used previously developed simulations of HIV screening [Paltiel, NEJM, 2005] and HIV treatment [Freedberg, NEJM, 2001] to project individual-level QALYs and costs for one-time and repeated rapid HIV screening. We linked these projections to published data on HIV transmission risks, with and without antiretroviral therapy (ART). We incorporated model-based estimates of discounted lifetime costs ($304,000) and QALY losses (10.8) attributable to new HIV infections. To describe the overall effect of ART on HIV transmission, we estimated intervention-specific values of R₀, the basic reproductive number (baseline values = 1.27 to 1.59 secondary transmissions per infected individual), a widely recognized summary measure of the persistence of an epidemic.

Results. Across a range of screening frequencies in a high-risk population, the cost-effectiveness of HIV screening depends critically on the assumed effects of ART on secondary HIV transmission (see Table), a parameter for which current evidence is mixed. In lower-risk populations, any repeated screening strategies are dominated unless the ART impact on transmission is favorable.

Conclusions. When population-level effects are taken into account, the attractiveness of expanded HIV screening hinges on the assumed transmission of infection with available therapy. While better estimates are needed, these findings suggest that effective risk-reduction counseling programs may be necessary components of any successful HIV screening intervention.