Background: Previous cohort studies have demonstrated the beneficial effects of antiretroviral therapy (ART) on viral load suppression. We aimed to examine the factors associated with virologic suppression for HIV-infected patients on ART receiving care at the Evandro Chagas Clinical Research Institute, Oswaldo Cruz Foundation in Rio de Janeiro, Brazil.
Methods: HIV-1 RNA levels and CD4+ T-cell counts at the date closest to midyear (1 July) were evaluated for 1,678 ART-naïve patients ≥ 18 years of age initiating ART between 1997 and 2010. The odds ratios (OR) and 95% confidence intervals (CI) for having an undetectable viral load (≤ 400 copies/mL) were estimated using generalized estimating equations regression models adjusted for clinical and demographic factors. Time-updated covariates included age, years since HIV diagnosis, hepatitis C diagnosis and ART interruptions.
Results: Between 1997 and 2011, the proportion of patients with an undetectable viral load increased from 6% to 78% and the median [interquartile range] CD4+ T-cell count increased from 207 [162, 343] to 554 [382, 743] cells/μL. Pre-treatment median CD4+ T-cell count significantly increased over the observation period from 114 [37, 161] to 237 [76, 333] cells/μL (p < .001). The per-year adjusted OR (aOR) for having undetectable viral load was 1.18 (95% CI = 1.16-1.21). ART interruptions >1 month per calendar significantly decreased the odds [aOR = 0.32 (95% CI = 0.27-0.38)] of having an undetectable viral load. Patients initiating on a protease inhibitor (PI)-based first-line regimen were less likely to have undetectable viral load [aOR = 0.72 (95% CI = 0.63-0.83)] compared to those initiating on a non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimen.
Conclusions: Our results demonstrate significant improvements in virologic outcomes from 1997 to 2011, which persisted after adjusting for other factors. This may in part be due to improvements in care and new treatment options. NNRTI- versus PI-based first-line regimens were found to be associated with increased odds of having an undetectable viral load, consistent with previous studies. Treatment interruptions were found to be the most important determinant of not having an undetectable viral load. Studies are needed to characterize the reasons for treatment interruptions and to develop subsequent strategies for improving adherence to ART.