The use of banner ads through the DM method was highly successful during both rounds of WHBS data collection. The systematic sampling methods used in the WHBS pilot were less successful but produced important insights regarding the feasibility of these methods. We found that a VBS method designed to approximate the methods used for real-world venues by NHBS was theoretically feasible using internet “venues”, but was labor-intensive, had difficulty meeting adequate enrollment proportions, and did not capitalize on some of the benefits of an internet-based sampling method (e.g., enrollment required a staff recruiter and was not automated). VBS is particularly complicated due to rapid changes in internet technology and the fluctuation of sites most commonly used by MSM for networking and socializing. RDS is another potentially viable systematic sampling option for the internet, but in both rounds of WHBS data collection, we were unable to sustain the necessary peer recruitment. RDS may not have been successful for WHBS because of the lack of incentives or the potentially weak ties between individuals of internet-based social networks; dual incentives and a strongly connected peer network have been recognized as potential preconditions for RDS success [18
]. Another internet-based research survey did successfully use RDS to recruit a sample of college students, but this success may have been supported by real-world connections between peers in that study [23
DM resulted in a large sample of eligible MSM enrolled in a very brief period of time. These results are consistent with the experiences of several other research studies of MSM on the internet that used banner ad recruitment [7
]. With the exception of residency-based criteria, the eligibility, enrollment, and completion rates for DM were somewhat comparable to the other WHBS methods and the few other internet-based MSM behavioral studies that have reported recruitment information [5
]. Exclusive of the large number of persons ineligible because of residency, the eligibility rate, enrolment rate, and proportion who reported male-male sex in the past 12 months are consistent with the 2003-2005 MSM cycle of NHBS [3
], though the survey completion rate was substantially lower for the 2007 DM method of WHBS (67%) than for NHBS (93%). The overall average click-through rate (those screened among all impressions) for WHBS banner ads was equivalent to the industry average of 0.2%, but ads on MSM-specific websites, such as Manhunt.net and BGCOnline.com (formerly BlackGayChat) did substantially better [27
]. The refined DM method used in 2007 was also much more successful than the 2006 DM method at reaching racial/ethnic minority MSM and young MSM, both groups of importance to the MSM HIV epidemic and HIV behavioral surveillance.
Several limitations for the WHBS pilot study should be noted. We were unable to provide participant incentives in either round of data collection; participant incentives may be an integral part of the success of some systematic sampling methods (RDS in particular) and may have adversely impacted the success of these methods. We are unable to determine sampling bias or external validity for any of the WHBS samples. Because of the variability in the way that recruitment information was collected through different sampling methods, some of the differences in screening, eligibility, and enrollment rates may be due to the way information was collected and not to true differences between sampling methods. Because of the anonymous nature of the survey, we are also unable to determine whether an individual participated in the survey multiple times which may have been more feasible with the DM method, but we believe this would be minimized given the lack of incentives for survey participation. We also cannot determine the veracity of responses to survey questions, though social desirability bias is likely minimized by the anonymous nature of the survey. Finally, the sample sizes for VBS and RDS were inadequate for us to conduct statistical comparisons between the samples of MSM with an appropriate degree of scientific rigor, but this was also not the intent of this analysis, which was to determine the feasibility of the methods to reach target sample sizes.
The way in which MSM interact and seek sexual partnerships has expanded to include the internet, and as such, an internet-based sampling method for MSM has a role in monitoring HIV-related risk behavior. The WHBS pilot project has shown that an internet-based systematic sampling method of MSM is complex and may not be feasible, but obtaining a convenience sample of MSM using banner ads is feasible and may produce useful and timely behavioral information from a large number of MSM. Another paper published in this journal issue examines whether MSM surveyed through this sampling method differ from NHBS and explores whether internet-based sampling methods may have a role in providing behavioral surveillance information that is comparable or complementary to NHBS [17
]. Any future plans for internet-based sampling of MSM will need to account for the current state of internet technology and social networking to best capitalize on the internet as an HIV research, surveillance, and prevention tool.
Human Participant Protection
The WHBS pilot project was research conducted in compliance with federal regulations governing protection of human subjects and was reviewed and approved by all relevant human subjects review boards.