Optimizing the Timing of HIV Screening as Part of Routine Medical Care.

US federal guidelines recommend that medical providers test all adolescents and adults for HIV infection at least once before the age of 64. The wide age range included in these guidelines may limit their utility and impact. We created an arithmetic model to estimate how HIV screening at different ages would impact the total number of years of undiagnosed HIV infection in the population and the number of persons developing clinical manifestations of HIV/AIDS. Our base case model assumed that age of infection in the screened population was the same as the estimated age of infection among all persons diagnosed with HIV in the United States in 2010. We parameterized a second model assuming age of infection was similar to the younger age distribution observed in African Americans. In the base case model, the number of years of undiagnosed HIV infection and number of persons with clinical manifestations of HIV/AIDS were both minimized by screening at age 34. If age of infection was similar to that estimated to occur among African Americans, testing at age 24 and 27 would minimize the number of years of undiagnosed infection and clinical cases, respectively. For both parameterization scenarios, testing between the ages of 21 and 38 resulted in outcomes within 10% of the model's estimated optimal age for screening. Focusing HIV screening on a narrower age range than is currently recommended may improve the impact of routine HIV screening efforts.