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Background:  In therapy-naïve patients, immunologic and virologic responses at 6 months of HAART are important predictors of progression to AIDS. In this study, we assessed predictors of virologic response 6 months after initiation of HAART in a cohort of HIV-infected patients in a developing setting.

Methods:  Treatment-naïve patients who started HAART in Porto Alegre, Brazil, between January 1996 and November 2003 and had information on viral load at 6 months were included in this analysis. Demographic, antiretroviral regimen, adherence, prior AIDS diagnosis (according to CDC-revised criteria), CD4 cell count and viral load at baseline and after 6 months on therapy were among the variables analyzed. Virologic failure was defined as viral load level ≥ 400 copies/mL. Univariate analyses were performed by using χ² or Fisher’s exact test for categorical and Student’s t-test or Wilcoxon test for continuous variables. Variables with p < 10 in univariate analysis were included in the multivariate analyses.

Results:  Of 454 patients included in this study, 127 (27.9%) had virologic failure at 6 months. In the univariate analysis, virologic failure was associated with younger age (median 34 vs 37; p = 0.003), prior AIDS diagnosis (RR 1.18; 95% CI 1.05 to 1.30; p = 0.0089), higher baseline viral load (median 5.34 vs 5.00; p = 0.0002), lower baseline CD4 count (median 86 vs 182; p = 0.006), nonadherence (RR 1.39; 95% CI 1.16 to 1.68; p < 0.0001), regimen containing a single protease inhibitor, as compared with ritonavir-boosted regimens (OR 8.58; 95% CI 3.53 to 20.85; p < 0.0001), and therapy started before 1999 (p < 0.0001). To minimize the systematic effect of therapy indication and year of initiation, we analyzed the subset of patients with CD4 count ≤ 200 cells/mL who started therapy after 1999 (n = 158). After adjusting for age, education, adherence, regimen, and baseline viral load, nonadherence (OR 8.78; 95% CI 1.49 to 51.80; p = 0.0164), and <5 years of formal education (OR 6.05; 95% CI 1.02 to 35.99; p = 0.0479) remained independently associated with virologic failure.

Conclusions:  In this cohort, virologic success was associated with year of therapy initiation, consistent with the introduction of non-nucleoside reverse transcriptase inhibitors and ritonavir-boosted regimens into clinical practice. With currently available therapies, adherence and education were shown to be predictors of virological response, particularly in patients with more advanced immune deficiency.

Keywords: Highly Active Antiretroviral Therapy; Virological Failure; Adherence