RT Journal Article SR Electronic T1 Recommendations for clinical research in children presenting to primary care out-of-hours services: a randomised controlled trial with parallel cohort study JF BJGP Open JO BJGP Open FD Royal College of General Practitioners SP bjgpopen20X101154 DO 10.3399/bjgpopen20X101154 VO 5 IS 2 A1 Anouk AH Weghorst A1 Gea A Holtman A1 Pien I Wolters A1 Heleen A Russchen A1 Freek Fickweiler A1 Henkjan J Verkade A1 Johan Post A1 Karin M Vermeulen A1 Boudewijn J Kollen A1 Irma J Bonvanie A1 Marjolein Y Berger YR 2021 UL http://bjgpopen.org/content/5/2/bjgpopen20X101154.abstract AB Background Research in primary care is essential, but recruiting children in this setting can be complex and may cause selection bias. Challenges surrounding informed consent, particularly in an acute clinical setting, can undermine feasibility. The off-protocol use of an intervention nearing implementation has become common in pragmatic randomised controlled trials (RCTs) set in primary care.Aim To describe how the informed consent procedure affects study inclusion and to assess how off-protocol medication prescribing affects participant selection in a paediatric RCT.Design & setting A pragmatic RCT evaluating the cost-effectiveness of oral ondansetron in children diagnosed with acute gastroenteritis (AGE) in primary care out-of-hours services and a parallel cohort study.Method Consecutive children aged 6 months to 6 years attending primary care out-of-hours services with AGE were evaluated to assess the feasibility of obtaining informed consent, the off-protocol use of ondansetron, and other inclusion and exclusion criteria.Results The RCT's feasibility was reduced by the informed consent procedure because 39.0% (n = 325/834) of children were accompanied by only one parent. GPs prescribed ondansetron off-protocol to 34 children (4.1%) of which 19 children were eligible for the RCT. RCT-eligible children included in the parallel cohort study had fewer risk factors for dehydration than children in the RCT despite similar dehydration assessments by GPs.Conclusion The informed consent procedure and off-protocol use of study medication affect the inclusion rate, but had little effect on selection. A parallel cohort study alongside the RCT can help evaluate selection bias, and a pilot study can reveal potential barriers to inclusion.