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.
Keywords: HIV; MSM; gay; internet; sex..