Factors associated with virological suppression among HIV-positive individuals on highly active antiretroviral therapy in a multi-site Canadian cohort

OBJECTIVE: The aim of the study was to evaluate time to virological suppression in a cohort of individuals who started highly active antiretroviral therapy (HAART), and to explore the factors associated with suppression. METHODS: Eligible participants were HIV-positive individuals from a multi-site Canadian cohort of antiretroviral-naïve patients initiating HAART on or after 1 January 2000. Viral load and CD4 measurements within 6 months prior to HAART initiation were assessed. Univariate and multivariate analyses were conducted using piecewise survival exponential models where time scale was divided into intervals (<10 months; ≥10 months). Virological suppression was defined as the time to the first of at least two consecutive viral load measurements <50 HIV-1 RNA copies/mL. RESULTS: A total of 3555 individuals were included in the study, of median age 40 years [interquartile range (IQR) 34-47 years]. Eighty per cent were male, 18% had a history of injecting drug use (IDU), and 13% presented with an AIDS-defining illness at baseline. The median time to suppression was 4.55 months (IQR 2.99-7.89 months). In multivariate analyses, older age, male sex, treatment in Ontario rather than British Columbia, non-IDU history, and having an AIDS diagnosis at baseline predicted increased likelihood of suppression. Patients with low baseline viral load were more likely to have suppression [4-5 log(10) copies/mL, hazard ratio (HR) 1.27, 95% confidence interval (CI) 1.18-1.38; <4 log(10) copies/mL, HR 1.49, 95% CI 1.32-1.68] than patients with baseline viral load ≥5 log(10) copies/mL; however, this effect ceased after 18 months of follow-up. Suppression was more likely with nonnucleoside reverse transcriptase inhibitors and ritonavir-boosted HAART. CONCLUSION: Identification of patients at risk for diminished likelihood of virological suppression will allow focusing of efforts and the utilization of resources to maximize the benefits of HAART.