Respondent-driven sampling (RDS), a network-based method used to recruit hidden populations, is prone to bias. "However, these biases could facilitate recruitment of high-risk networks," according to the authors, who examined recruitment patterns of HIV-positive injection drug users (IDUs) and identified factors associated with being recruited by an HIV-positive IDU in an RDS-based study.
In Tijuana, RDS was used to recruit resident IDUs, age 18 and older, who reported injecting the previous month. Participants underwent interviews and testing for HIV, syphilis, and tuberculosis. Predictors of being recruited by an HIV-positive IDU were identified using weighted logistic regression.
Among the 1,056 IDUs, HIV-positive persons comprised 4.4 percent of the sample and generated 4.7 percent of recruits, "indicating that recruitment effectiveness did not vary by HIV status," the authors wrote. "However, 10 percent of the subjects recruited by HIV-positive recruiters were infected with HIV as compared to 4.1 percent of subjects recruited by HIV-negative recruiters (P=0.06), a difference that, after controlling for whether the recruiter and recruit injected drugs together, attained statistical significance (P=0.04), indicating that recruitment patterns differed by HIV status."
The researchers' analysis found that factors independently associated with being recruited by an HIV-positive IDU included lifetime syphilis infection, ever having sex with an HIV-positive person, knowing someone with HIV/AIDS, being recruited at a location where drugs are injected, recent use of a needle-exchange program, and a larger number of recent arrests for having track marks.
"HIV-positive IDUs have different recruitment patterns than HIV-negative IDUs, with HIV-positive IDUs tending to recruit other HIV-positive IDUs," the authors concluded. "Social and environmental factors along with risk behaviors were independently associated with being the recruit of an HIV-positive IDU in Tijuana. Although the goal of this study was not to recruit HIV-positive or other high-risk persons, our results suggest that RDS has the potential to successfully be used in the identification of HIV-positive or other high-risk individuals."