Recruitment-Adjusted Estimates of HIV Prevalence and Risk among Men Who Have Sex with Men: Effects of Weighting Venue-Based Sampling Data

Background: Venue-based sampling (VBS) is a quasi-probability study design widely used to estimate disease prevalence and risk factors among groups such as men who have sex with men (MSM) congregating at known venues. However, VBS-related recruitment biases have not been adequately explored and adjusted for in previous literature. Methods: In a 2008 VBS study of 479 self-reported HIV-negative MSM in New York City, we compared crude estimates of HIV risk factors and seroprevalence to estimates weighted to address the lower selection probabilities of MSM who attend social venues infrequently or were recruited at high-volume venues. Results: Our approach rates (MSM approached/MSM counted) were lowest at dance clubs, gay pride events, and public sex strolls where venue volumes were highest; response rates (MSM interviewed/MSM approached) ranged from 39% at pride events to 95% at community-based organizations. Over the past year, 49% attended gay-oriented social venues at least weekly and 21% once a month or less. In estimates adjusted for these variations, the prevalence of several past year risk factors (unprotected anal intercourse with a casual partner, 5 or more total partners, at least weekly binge drinking, and hard drug use) were significantly lower compared to crude estimates. Adjusted HIV prevalence was lower (14.8% vs. 17.5%), but not significantly. Conclusions: Not adjusting VBS data for inherent recruitment biases could overestimate HIV prevalence and risk factors when the selection probability is greater for higher-risk MSM. While further examination of recruitment-adjustment methods for VBS data is needed, presentation of both unadjusted and adjusted estimates is currently suggested.