Retaining traditionally hard to reach participants: Lessons learned from three childhood obesity studies.

Retaining underserved populations, particularly low-income and/or minority participants in research trials, presents a unique set of challenges. In this paper, we describe the initial retention strategies and enhanced the retention strategies over time across three childhood obesity prevention trials. Hip-Hop to Health Jr. (HH) was a randomized controlled trial (RCT) testing a preschool-based obesity prevention intervention among predominately African-American children. Retention was 89% at 14-weeks, 71% at 1-year, and 73% at 2-year follow-up. Primary retention strategies for HH included: 1) collaboration with a community-based organization to enhance program credibility; 2) continuity of data collection locations; 3) collecting detailed contact information and provision of monetary compensation; and 4) developing a detailed tracking/search protocol. In a follow-up trial, Hip-Hop to Health Jr. Obesity Prevention Effectiveness Trial (HH Effectiveness), 95% of participants completed assessment at 14 weeks and 88% completed assessment at 1 year. For this trial, we emphasized staffing continuity in order to enhance participant relationship building and required data collection staff to have relevant community service experience. In a third study, we assessed dietary quality among participants in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) across three time points following the WIC food package shift instituted nationally in 2009. Retention rates were 91% at 12 months and 89% at 18 months. For our WIC\ study, we augmented retention by developing a home data collection protocol and increased focus on staff diversity training. We conclude with a summary of key strategies and suggestions for future research.