We investigated the current success of early HIV detection in Australia and the likely effectiveness of Treatment as Prevention.
HIV diagnoses data from the Australian National HIV/AIDS Registry were analyzed for CD4 T-cell counts at diagnosis and for prior HIV testing. Mathematical modeling based on these data estimated future HIV prevalence and incidence under different scenarios of antiretroviral therapy (ART) usage.
CD4 T-cell counts significantly decreased with age (P < 0.0001) for men who have sex with men (MSM) and women in all HIV diagnoses, and for diagnoses at primary HIV infection (P < 0.02). This decrease with age meant that >50% of MSM aged 29 years and older are diagnosed with a CD4 T-cell count <500 cells per cubic millimeters. Diagnosis during primary HIV infection has stabilized at 15% for MSM, with a lower percentage for older individuals (P = 0.002), but only 5% of women were diagnosed at this early stage. MSM older than 50 years were significantly less likely to have had an HIV test before diagnosis (P < 0.0001), whereas women of all ages at HIV diagnosis were less likely to have been tested than MSM. Mathematical modeling indicated that current levels of ART would see a continuing increase in HIV diagnoses among MSM. A 90% ART enrollment would result in an almost immediate decline in prevalence and would be cost effective in terms of person-years on ART by 2028.
Treatment as Prevention would be an effective intervention in Australia and other developed countries.