Reductions in HIV prevalence rates among substance-using men who have sex with men in Los Angeles County, 2008-2011.

An outreach program performed street encounters with 5,599 unique substance-using MSM from January 2008 through December 2011. HIV prevalence reduced from 20.2% in the first half of 2008 to 8.1% in the second half of 2011. Older, gay-identified, non-Hispanic/Latino participants were each more likely to report a HIV-positive serostatus. When controlling for these cofactors, robust log-Poisson analysis revealed that each additional day of methamphetamine (RRR = 1.03; 95% CI [1.02, 1.03]) and/or marijuana (RRR = 1.01; 95% CI [1.01, 1.02]) use in the previous 30 days, injection drug use at any point in their lifetime (RRR = 2.01; 95% CI [1.70, 2.37]), and/or unprotected anal intercourse with another male in the previous 30 days (RRR = 1.48; 95% CI [1.29, 1.71]) were associated with HIV-positive status. When controlling for all these cofactors, the probability of reporting a HIV-positive status reduced an estimated 9% (95% CI [6%, 12%]) every six months throughout the reporting period. Self-reported HIV prevalence decreased among this sample of substance-using MSM in LAC from 2008 to 2011.