Background: Several recent studies have shown that the combination of ddI plus TDF can produce an unexpected drop in CD4 cell counts, even after correcting the ddI dose.
Objective: Comparative study of the immunological effectiveness of various once-daily NRTI backbones (ddI plus TDF, ddI plus 3TC or TDF plus 3TC) in antiretroviral-experienced HIV-infected patients achieving viral suppression (PCR, HIV-RNA < 50 copies/microl).
Methods: Prospective cohort study of 48 weeks' duration following viral load suppression with any of the NRTI combinations studied. The main outcome variable was the increase in CD4+ lymphocyte count from the time that viral load was undetectable or treatment was changed for simplification or toxicity (baseline) up to 48 weeks of follow-up. Differences between the assigned therapies were compared. The variables included in analysis were age, sex, risk group, HCV infection, clinical categories of HIV (CDC criteria), lowest CD4 cell count, reason for change of NRTI backbone, type of antiretroviral treatment (PI, NNRTI, or 3 NRTI) and duration of suppressed viral load. RESULTS. Regimens including ddI plus TDF showed significant decreases in CD4 cell counts with adjustments by type of HAART, reason for change, and duration of suppressed viral load. In patients treated with TDF + 3TC, CD4 count increased by 160 cel/microl (95% CI, 53-266) more than in patients treated with TDF + ddI; and in patients receiving ddI + 3TC, CD4+ count increased by 138 cel/microl (95% CI, 25-266) more than in patients receiving TDF + ddI.
Conclusions: The ddI plus TDF backbone seems unadvisable because of the lower associated CD4 cell counts, and because it is poorer than the other options from the immunological standpoint.