Assessing the effectiveness of antiretroviral regimens in cohort studies involving HIV-positive injection drug users.

OBJECTIVE: We compared the effectiveness of different highly active antiretroviral therapy (HAART) regimens considering, separately, history of injection drug use (IDU) (yes/no). DESIGN,
METHODS: A total of 1163 HIV-infected patients initiated HAART between 1 January 2000 and 28 February 2009 in British Columbia, Canada, and were followed until 28 February 2010. HAART effectiveness was measured by the ability to achieve viral suppression below 50 copies/ml at 6 months. We compared HAART regimens containing efavirenz and boosted atazanavir. We developed logistic regression models using different techniques to control for potential confounders.
RESULTS: Among the 1163 patients, 796 (68%) achieved viral suppression at 6 months (32% reporting a history of IDU). Different confounding models yielded very similar odds ratios for achieving viral suppression. Boosted atazanavir-based HAART demonstrated to be the most effective regimen, showing a surprisingly higher benefit for patients with a history of IDU (odds ratios from different models ranged from 1.74-1.95 to 1.45-1.51).
CONCLUSIONS: The literature has conflicting results regarding the effectiveness of HAART to treat HIV infection among those with a history of IDU. We have shown that most patients, with and without a history of IDU, were able to achieve viral suppression at 6 months. Boosted atazanavir-based HAART was the most resilient regimen and it was more effective than efavirenz-based HAART among IDUs. Given the limited inclusion of IDU in clinical trials of HAART's efficacy, a randomized clinical trial comparing different first-line HAART regimens among IDU is warranted based on these results.