Objective: To compare the rate of disease progression according to viral load and CD4 cell count in patients receiving or not receiving highly active antiretroviral therapy (HAART), defined as protease inhibitor-containing regimens.
Design: An observational study, with prospectively collected data.
Methods: All patients attending the HIV Outpatient clinic as of 1 January 1995 (n = 2083) were included. Follow-up was until the first AIDS-defining event or death. Associations between viral load or CD4 cell count and disease progression were assessed using a person-years approach. Event rates were compared using Poisson regression analysis; a multivariate model was used to assess the independent effects of CD4, viral load and treatment group on event rates and to consider interactions between these variables.
Results: The event rates increased with lower CD4 cell count and higher viral load for both treatment groups and were generally lower in the HAART group. In a multivariate analysis, lower CD4 cell counts and higher viral loads remained significantly associated with disease progression, irrespective of treatment group. However, the event rate was significantly lower for the HAART group compared with the control group (relative rate 0.53, P < 0.001).
Conclusions: HAART-treated patients with high viral loads and CD4 cell counts experienced reduced disease progression compared with individuals with the same CD4 cell count and viral load not receiving HAART. Consequently, the short-term prognosis associated with viral load levels and CD4 cell counts may differ in patients on HAART. Whether this effect will be observed with non-protease-inhibitor-containing HAART is not known at this time.