Differences between Internet and community samples of MSM: implications for behavioral surveillance among MSM in China.

This study compared the difference between two samples of men who have sex with men (MSM) in Harbin, China, using cross-sectional data that were collected via the Internet and through conventional venue-based outreach. All participants in both samples lived in or nearby Harbin in northeast China. Results showed that the Internet sample was significantly younger, more educated and more likely to be students and to self-identify as homosexual than the community sample. After controlling for demographic characteristics, the community sample was more likely to have had sex with females (OR 2.01, CI 1.22-3.30, p=0.006) and to have had > or =6 male partners in the previous six months than the Internet sample (OR 4.88, CI 3.51-6.80, p<0.001). No significant difference was observed in the prevalence of unprotected anal intercourse, exchanging sex for money, exchanging money for sex or illicit drug use between the two samples. For those seeking sex both on the Internet and in traditional gay venues, participants in the community sample were nearly three times more likely to have had > or =6 male partners during the previous six months than those in the Internet sample (p=0.001). In conclusion, the online and offline samples of MSM are significantly different and carry different levels of risk for HIV transmission. Using the Internet as a data collection method may serve as an additional mechanism for the existing gay venue-based behavioral surveillance system in China.