Participant retention in paediatric randomised controlled trials published in six major journals 2015-2019: systematic review and meta-analysis.

Published paediatric RCTs rarely report the use of specific modifiable factors that improve retention. Including multiple, regular follow-ups with participants before the primary outcome may reduce attrition. Retention may be highest when the primary outcome is collected up to 6 months after a participant is recruited. Our findings suggest that qualitative research into improving retention when trials involve multiple participants such as young people, and their caregivers or teachers would be worthwhile. Those designing paediatric trials also need to consider the use of appropriate engagement methods. RESEARCH ON RESEARCH (ROR) REGISTRY: https://ror-hub.org/study/2561.