Respondent driven sampling: an innovative way to access hard-to-reach populations in the conservative culture of Egypt
Background: A new form of chain-referral sampling, called respondent driven sampling (RDS), is used to sample hidden populations. It resolves the dilemma between coverage and statistical validity by making chain-referral into probability sampling. Egypt has taken the lead in the region in implementing a Biological and Behavioral Surveillance Survey (BIO-BSS) and examining the use of RDS. This paper shares operational procedures, strengths, and limitations of RDS in Egypt.
Methods: Egypt’s BIO-BSS used RDS to reach male and female injection drug users (IDUs) and men who have sex with men (MSM). It targeted 25 seeds for each group at the inception phase. Others were added later. Only five female IDU seeds were identified. Seeds were asked to recruit three of their peers who were then asked to recruit three others. A coupon management system was put in place to link recruiters to recruitees. The study included four different interview questionnaires. Interviewers were members of high-risk groups, except for the female IDUs. A monitoring and evaluation plan was established. Data was managed using RDS software.
Results: For male IDUs and MSM, recruitment progressed actively. Eight male IDU seeds and five MSM seeds reached four waves of respondents. Most recruited people close to them. Estimated HIV seroprevalence was similar to that of the sample; however, the 95% confidence interval was very wide. RDS failed to reach female IDUs, who appear not to network with the same sex, and few female respondents were recruited by male peers. The study was plagued by duplicates and imposters who were easily handled by interviewers. The strength of RDS is that it reached male hidden populations quickly. However, it required training and careful planning and supervision during implementation.
Conclusions: RDS is feasible but requires formative research to understand the target population, especially in a conservative culture like Egypt.
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