Respondent Driven Sampling Method of Recruitment for a Case Control Study of Gastric Cancer Risk.

Gastric cancer (GC) disproportionately affects ethnic minorities in the US including Asians and Pacific Islanders. Research with minority groups who are at high risk are needed to provide more effective treatment. Successful recruitment of minorities to research must overcome obstacles of language, access, fear and mistrust. Respondent Driven Sampling (RDS) is a sampling strategy designed to recruit underrepresented minority populations using social networks. However, there are no reports of RDS being used for a case-control study. Our pilot study examined the feasibility of using RDS as a recruitment strategy to enroll a large number of participants to develop a GC screener. Our preliminary work showed that 750 cases and 5,250 controls would be needed to fully develop this tool. GC cases, who also served as the seeds, were asked to refer 2 more people to participate as controls in our study. Our pilot goal was to recruit 8 GC cases (as seeds) and 112 controls using three waves of referrals and recruitment. Twenty-seven GC cases were contacted of which 10 refused, 4 expressed interested to participate in the survey but were unwilling to recruit controls. Thirteen cases were recruited but only 5 Complete the survey. Of these 5, 3 cases did not pass on referral coupons and only 2 of the participants gave coupons to 3 potential controls. Our study revealed the limitations of using RDS with cancer patients to support recruitment. GC patients' constrained social networks, inadequate incentives or other factors may have contributed to the lack of success with using RDS in this setting.