WHO SHOULD BE SCREENED FOR HIV-INFECTION - A COST-EFFECTIVENESS ANALYSIS

Background: The advent of effective prophylactic treatments for asympt omatic persons infected with human immunodeficiency virus has led to i nterest in widespread screening programs. However, the costs of screen ing programs and therapy are high, and the prevalence of infection abo ve which screening becomes an appropriate use of scarce health care do llars remains undetermined. Methods: 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 t wo strategies: (1) screening and prophylactic treatment for infected p ersons who have or who develop low CD4+ (T4) cell counts, and (2) no s creening. Based on studies in-the literature, we estimated the prevale nce of HIV infection, the rate of T4-cell loss, the rates of developin g the acquired immunodeficiency syndrome and Pneumocystis pneumonia st ratified by T4 cell counts, the life expectancy with the acquired immu nodeficiency syndrome, the efficacy of prophylactic therapies, and cos ts. Results: 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 ef ficacy of zidovudine is assumed to be limited to 3 years, screening st ill 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 lo w 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. Conclusion: When considering only direct medical benefits, screening for asymptoma tic 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 th e range of currently accepted medical practices. These results suggest that screening be offered routinely to all persons in defined populat ions, such as persons receiving care at hospitals or clinics, or resid ing in geographic areas, where the seroprevalence is 0.5% or more, and underscore the need to conduct seroprevalence studies to identify suc h populations.