How Much Should We Pay for a New HIV Diagnosis? A Mathematical Model of HIV Screening in US Clinical Settings

Objective. To develop a model to assist clinical setting decision makers in determining how much they can spend on human immunodeficiency virus (HIV) screening and still be cost-effective. Design. The authors developed a simple mathematical model relating the program cost per new HIV diagnosis to the cost per HIV infection averted and the cost per quality-adjusted life year (QALY) saved by screening. They estimated outcomes based on behavioral changes associated with awareness of HIV infection and applied the model to US sexually transmitted disease clinics. Methods. The authors based the cost per new HIV diagnosis (2009 US dollars) on the costs of testing and the proportion of persons who tested positive. Infections averted were calculated from the reduction in annual transmission rates between persons aware and unaware of their infections. The authors defined program costs from the sexually transmitted disease clinic perspective and treatment costs and QALYs saved from the societal perspective. They undertook numerous sensitivity analyses to determine the robustness of the base case results. Results. In the base case, the cost per new HIV diagnosis was $2528, the cost per infection averted was $40,516, and the cost per QALY saved was less than zero, or cost-saving. Given the model inputs, the cost per new diagnosis could increase to $22,909 to reach the cost-saving threshold and to $63,053 for the cost-effectiveness threshold. All sensitivity analyses showed that the cost-effectiveness results were consistent for extensive variation in the values of model inputs. Conclusions. HIV screening in a clinical setting is cost-effective for a wide range of testing costs, variations in positivity rates, reductions in HIV transmissions, and variation in the receipt of test results.