Design and strategies used for recruitment and retention in a double blind randomized controlled trial investigating the effects of soluble corn fiber on bone indices in pre-adolescent children (PREBONE-Kids study) in Malaysia

Abstract

Background Recruitment and retention in longitudinal nutrition intervention studies among children is challenging and scarcely reported. This paper describes the strategies and lessons learned from a 1-year randomized double-blind placebo-controlled trial among pre-adolescent children on the effects of soluble corn fiber (SCF) on bone indices (PREBONE-Kids). Methods Participants (9–11 years old) were recruited and randomized into 4 treatment groups (600 mg calcium, 12 g SCF, 12 g SCF plus 600 mg calcium and placebo). Interventions were consumed as a fruit-flavored powdered drink for 1-year. School-based recruitment was effective due to support on study benefits from parents and teachers, peer influence and a 2-weeks study run-in for participants to assess their readiness to commit to the study protocol. Retention strategies focused on building rapport through school-based fun activities, WhatsApp messaging, providing health screening and travel reimbursements for study measurements. Compliance was enhanced by providing direct on-site school feeding and monthly non-cash rewards. Choice of 2 flavors for the intervention drinks were provided to overcome taste fatigue. Satisfaction level on the manner in which the study was conducted was obtained from a voluntary sub-set of participants. Results The study successfully enrolled 243 participants within 6 months and retained 82.7% of the participants at the end of 1 year, yielding a drop-out rate of 17.3%. Compliance to the intervention drink was 85% at the start and remained at 78.7% at the end of 1 year. More than 95% of the participants provided good feedback on intervention drinks, rapport building activities, communication and overall study conduct. Conclusion Successful strategies focused on study benefits, rapport building, frequent communication using social media and non-cash incentives helped improved compliance and retention rate. The lessons learned to maintain a high retention and compliance rate in this study provide valuable insights for future studies in a similar population.