Who should be screened for HIV infection? A cost-effectiveness analysis

The advent of effective prophylactic treatments for asymptomatic persons infected with human immunodeficiency virus has led to interest in widespread screening programs. However, the costs of screening programs and therapy are high, and the prevalence of infection above which screening becomes an appropriate use of scarce health care dollars remains undetermined.

To examine the cost-effectiveness of screening in populations with differing prevalences of infection, we developed a Markov model to compare costs and life expectancy for two strategies: (1) screening and prophylactic treatment for infected persons who have or who develop low CD4+ (T4) cell counts, and (2) no screening. Based on studies in the literature, we estimated the prevalence of HIV infection, the rate of T4-cell loss, the rates of developing the acquired immunodeficiency syndrome and Pneumocystis pneumonia stratified by T4 cell counts, the life expectancy with the acquired immunodeficiency syndrome, the efficacy of prophylactic therapies, and costs.

In populations with a prevalence of infection more than 5%, which includes known risk groups, screening costs less than $11,000 per life-year gained. In populations with a prevalence as low as 0.15%, screening costs only $29,000 per life-year gained. Even when the efficacy of zidovudine is assumed to be limited to 3 years, screening still costs less than $40,000 per life-year gained in populations with a prevalence of 0.5% or greater. However, in populations with a very low prevalence of infection (two to 10/100,000), such as members of the general population without reported risk factors, screening costs rise to between $290,000 and $1,277,400 per life-year gained.

When considering only direct medical benefits, screening for asymptomatic human immunodeficiency virus infection in the general population, without regard to reported risk factors or seroprevalence data, would be expensive. In populations with a prevalence of infection of 0.5% or greater, however, the cost-effectiveness of screening falls within the range of currently accepted medical practices. These results suggest that screening be offered routinely to all persons in defined populations, such as persons receiving care at hospitals or clinics, or residing in geographic areas, where the seroprevalence is 0.5% or more, and underscore the need to conduct seroprevalence studies to identify such populations.