Parametric modelling of survival following HIV and AIDS in the era of highly active antiretroviral therapy: data from Australia

Parametric survival models have not previously been applied to survival following a diagnosis of HIV/ AIDS in Australia. Four different parametric models—exponential, Weibull, log-normal and log-logistic—were applied to data both on HIV-positive cases and on cases diagnosed with AIDS collected through the national HIV/AIDS surveillance system. Using likelihood based goodness-of-fit criteria the Weibull model was found to be the best-fitted model for predicting survival following a diagnosis of HIV infection without and with a diagnosis of AIDS. Several covariates—age, sex, combined HIV exposure category, CD4 cell counts, antiretroviral treatment and AIDS-defining illnesses—were included in the parametric model to predict factors associated with future mortality. Predicted deaths were in agreement with the observed deaths following HIV infection and AIDS. The Weibull model will be applied for future projections of deaths from HIV/AIDS.