CD4 count and viral load time-courses in patients treated with highly active antiretroviral therapy and association with the CDC staging system

Objectives: The aim of the study was to analyse CD4 cell count and viral load dynamics in patients undergoing antiretroviral therapy and their association with the Centers for Disease Control and Prevention (CDC) classification system. Methods: CD4 cell count and viral load were determined in 2982 patients who were classified according to clinical and immunological CDC stages. Measurements were carried out at baseline and at the 3rd, 6th and 12th months. Results: Clear differences in the immunological and virological responses to therapy were observed depending on the CDC stage, with better results associated with less advanced stages. There was a marked parallelism in the CD4 cell count curves of the different CDC stages over the year of follow up, in both naïve and experienced patients, indicating that the increase in CD4 cell count at each time-point was similar for all clinical and immunological CDC stages. However, as the baseline values were closely associated with CDC stage, the CD4 cell counts finally reached were clearly dependent on CDC stage. The highest virological responses were observed during the initial 3 months, particularly in naïve patients, but whereas naïve patients showed additional increases up to the 6th month experienced patients reached a plateau at the 3rd month. The CD4 increases were also higher during the initial 3 months but persisted during the year of follow-up. Conclusion: Both clinical and immunological CDC stages at baseline are highly predictive of the immunological and virological response to therapy, a finding that could have clinical implications.