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Venue-Based Sampling in STD Research: Generalizeable to and Independent of Whom?

ELLEN, JONATHAN M. MD*; FICHTENBERG, CAROLINE M. PhD†

Sexually Transmitted Diseases: August 2007 - Volume 34 - Issue 8 - pp 532-533
doi: 10.1097/OLQ.0b013e318125660c
Editorial

From the *Division of General Pediatrics and Adolescent Medicine, Department of Pediatrics, Johns Hopkins School of Medicine; and †Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland

Correspondence: Jonathan M. Ellen, MD, Department of Pediatrics, Johns Hopkins School of Medicine, Mason F. Lord, Center Tower, 5200 Eastern Ave., Suite 4200, Baltimore, MD 21224. E-mail: jellen@jhmi.edu.

Received for publication May 11, 2007, and accepted May 24, 2007.

In this issue, Rothenberg and colleagues report on the prevalence of sexual behaviors and STIs, including gonorrhea, chlamydia, herpes, hepatitis C, and HIV, among a sample of youth, black, 15 to 18 years old, recruited through venue-based and network sampling approaches from working-class neighborhoods in Atlanta.1 The investigators found that approximately 15% to 20% of participants had been expelled from school, over 20% of the boys were selling drugs, and greater than 25% of the boys and girls had ever spent time in jail. On average, the boys had more than 4.5 sex partners in the past year and the girls had more than 1.5 sex partners in the past year. Most alarming were the high rates of chlamydia and gonorrhea among participants. Chlamydia infection rates among the boys and girls were approximately 13% and 27%, respectively, whereas gonorrhea rates were 2% and 11%, respectively. These rates are higher than national estimates2 and Healthy People 2010 goals.3

Many might be inclined to dismiss these findings as biased, however, because participants were not randomly and independently selected. Indeed, the investigators enrolled participants by directly approaching youth at 6 street-based venues, including a mall in a working-class neighborhood in southwest Atlanta. The venues were purposefully selected because they appeared to be high-traffic venues attended by age-eligible individuals. Every participant enrolled from the venues was asked to nominate at least 1 social, drug, or sexual contact for participation. A total of 512 participants were enrolled: 242 from the venues and 270 of their contacts. As would have been expected, many of the individuals recruited from a venue were linked to others recruited from the same venue. The number of dyads in the final sample was 991, which consisted of interconnected venue participants and venue participants and their enrolled contacts. As a result of this sampling design, it is difficult to argue that these results are generalizeable to a larger population.

We would argue, however, that this is the wrong way to think about this study, just as thinking about individuals in isolation is the wrong way to think about disease transmission. We believe instead that this study should be interpreted in the context of the growing body of literature illustrating the importance of factors beyond the individual in disease transmission.4 What this sample represents is a sample from the networks through which behaviors as well as infectious organisms are transmitted. As such, this study illustrates the way in which certain behaviors and pathogens cluster in certain socially and geographically defined groups. Although the study does not speak to the burden of risk borne by black youth nationally, it does tell us something very important about the burden of risk shouldered by certain communities and about the disparities that exist between different communities.

It is well known that STIs including HIV are not homogeneously distributed across geographic or social space in the United States. Rather, STIs cluster geographically and socially.2,5–7 It has further been argued that they cluster because social and sexual networks are shaped by structural features of the social and physical environment. Identified HIV/STI-related structural risks include segregation, homophobia, public sex venues, alcohol outlets, drug dealing venues, poorly performing schools, and high rates of incarceration.4 And, given that many of these structural risk factors are more prevalent within poor black communities or sexual minority communities, it logically follows that associated individual-level risk factors (e.g., concurrency, drug dealing, sex for money or drugs, multiple sex partners) and STIs cluster within these communities.

The argument presented above has implications for the interpretation of the report by Rothenberg and colleagues. First, the question of to whom are the findings generalizeable should not focus on the individuals but on communities. And, in this case, the answer is poor urban black communities in the Southern region of the United States that have a known high-risk prevalence of STI/HIV based on surveillance data. Furthermore, because individuals who reside in these communities are socially and, in some cases, sexually connected through networks, we believe that the nonindependence of the study participants is not a limitation of the study. Rather, it is an indication that the sampling tapped into a cohesive network through which disease is spread in a community.

From our perspective, the findings of Rothenberg and colleagues should not be ignored. To the contrary, we believe that the findings highlight the magnitude of HIV/STI for youth residing in similar communities around the country, and it is these communities that drive the disparities in HIV/STI. Their findings should heighten the sense of public health urgency to confront network and community-level structural factors that promote HIV/STI transmission.

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References

1. Rothenberg R, Hoang TDM, Muth SQ, et al. The Atlanta Urban Adolescent Network study: A network view of STD prevalence. Sex Transm Dis 2007; 34:525–531.
2. Centers for Disease Control and Prevention. STD Surveillance 2005: Special Focus Profiles. Online 2007.
3. Davis RM. Healthy People 2010: National health objectives for the United States. BMJ 1998; 317:1513–1517.
4. Ziff MA, Harper GW, Chutuape KS, et al. Laying the foundation for Connect to Protect (R): A multi-site community mobilization intervention to reduce HIVAIDS incidence and prevalence among urban youth. J Urban Health 2006; 83:506–522.
5. Ellen JM, Kohn RP, Bolan GA, et al. Socioeconomic differences in sexually-transmitted disease rates among black-and-white adolescents, San-Francisco, 1990 to 1992. Am J Public Health 1995; 85:1546–1548.
6. Ellen JM, Hessol NA, Kohn RP, et al. An investigation of geographic clustering of repeat cases of gonorrhea and chlamydial infection in San Francisco, 1989–1993: Evidence for core groups. J Infect Dis 1997; 175:1519–1522.
7. Jennings JM, Curriero FC, Celentano D, et al. Geographic identification of high gonorrhea transmission areas in Baltimore, Maryland. Am J Epidemiol 2005; 161:73–80
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