Age, adherence and injection drug use predict virological suppression among men and women enrolled in a population-based antiretroviral drug treatment programme.

Objectives: To characterize 1-year virological response to antiretroviral therapy and its determinants by sex.

Methods: This is a population-based analysis of antiretroviral therapy naive HIV-positive adult men and women. Factors associated with sex and with plasma HIV RNA viral load suppression to below 500 copies/ml were examined using non-parametric tests and logistic regression analyses.

Results: A total of 739 subjects (92 women and 647 men) were eligible. Female participants were younger (34 vs 37 years; P < 0.001), less likely to have AIDS (6.5 vs 14.4%; P = 0.039), more frequently injection drug users (44.6 vs 25.2%; P = 0.001) and were less likely to be adherent to therapy (34.8 vs 62.9%; P < 0.001) than male participants. There was no difference in baseline median CD4 count (P = 0.424) or HIV RNA levels (P = 0.140), physician experience (P = 0.057), or with respect to antiretroviral regimens containing protease inhibitors or non-nucleoside reverse transcriptase inhibitors (P = 0.911). With treatment, 46.7% (43/92) of women and 64.8% (419/647) of men (P = 0.001) suppressed HIV RNA viral load to below 500 copies/ml at 1 year. In a multivariate analysis, the association of sex with HIV RNA response to antiretroviral therapy fell from statistical significance (odds ratio 1.18; 95% CI: 0.72-1.95) after adjusting for adherence, injection drug use and age.

Conclusion: Our data indicate that in this population-based setting, sex differences in 1-year virological response to antiretroviral therapy are explained by age, adherence and injection drug use.