Internet-Based Methods May Reach Higher-Risk Men who have Sex with Men Not Reached Through Venue-Based Sampling§

BACKGROUND Internet-based sampling methods may reach men who have sex with men (MSM) who don't attend physical venues frequented by MSM and may be at higher risk of HIV infection. METHODS Multivariate logistic regression was used to examine characteristics of adult MSM participants in 2 studies conducted in the same 5 U.S. cities: the 2003-2005 National HIV Behavioral Surveillance System (NHBS) which used sampling from physical MSM venues (e.g., bars, clubs) and the 2007 Web-based HIV Behavioral Surveillance (WHBS) pilot which used sampling through online banner advertisements. RESULTS Among 5024 WHBS MSM, 95% attended a physical MSM venue in the past 12 months, and 75% attended weekly. WHBS MSM who were black, aged 18-21 years, not college educated, bisexual- or heterosexual-identifying, and reported unknown HIV serostatus were less likely to have attended a physical MSM venue in the past 12 months (all p<0.01). Compared to NHBS MSM, WHBS MSM were more likely to be white, younger, college-educated, report unknown HIV serostatus, report unprotected anal intercourse with a casual partner, and have first met that partner online (all p<0.0001). WHBS MSM were less likely to have been under the influence of drugs during most recent sex (p=0.01) or not know their sex partner's HIV serostatus (p<0.0001). CONCLUSIONS Many MSM recruited online also attended physical venues, but attendance varied by sub-group. Participants in WHBS and NHBS differed, and WHBS may represent a group of MSM at higher risk of HIV infection. These findings suggest that an internet-based method may be a useful supplement to NHBS.