Comparison of surveillance sample demographics over two cycles of the National HIV Behavioral Surveillance Project, Houston, Texas.

We examined differences in sample demographics across cycles of the National HIV Behavioral Surveillance project, that examines HIV risk behaviors among men who have sex with men (MSM), injection drug users (IDU), and heterosexuals living in areas of high HIV prevalence (HET). MSM were recruited through venue-based sampling, and IDU and HET through respondent driven sampling (RDS). RDS data were weighted to account for sampling bias. We compared crude prevalence estimates from MSM1 (2004) to those from MSM2 (2008) for demographic factors known to influence risky sexual and drug-use behaviors. We compared crude and adjusted prevalence estimates for IDU1 (2005) and IDU2 (2009) and HET1 (2006) and HET2 (2010). In the MSM cycle, we found differences in age, and the proportions seeking medical care and reporting a recent arrest. There were no differences in the comparison of crude and weighted estimates for the RDS collected samples, nor were there differences comparing HET1 and HET2 weighted estimates. IDU2 recruited a larger proportion of males, and had a higher percent who graduated from high school and who reported recent medical care and a previous HIV test. Differences across MSM cycles may be related to differences in venues identified for each cycle. Differences in the IDU cycles may be due to an effort on our part to increase the racial/ethnic and drug-use diversity of the sample in IDU2. Our findings show the importance of formative work for both venue-based and RDS samples to increase understanding of the dimensions that affect social networks and the dynamics of populations in space and time. With familiarity of the target population, we believe that both venue-based and RDS recruitment approaches for NHBS work well and can be used to evaluate changes in risky sexual and drug use behaviors and in HIV testing behaviors.