Background Clinical trial discontinuation represents a waste in research resources and raises ethical concerns. Conduct of clinical trials is perceived to be more challeng-ing in children than in adults. The aim of this study was to evaluate the impact of the age of participants on comple-tion rates of randomised controlled trials (RCTs).
Methods This is a cross-sectional study on RCTs regis-tered in the ClinicalTrials.gov database. All RCTs registered in the database from its inception date (February 29, 2000) to December 31, 2016, were extracted. RCTs with unknown recruitment status or registered more than 60 days after their start date were excluded. Remaining RCTs were classified according to their recruitment status: active, completed, and discontinued trials, and according to the age of participants: children (0–17 years), adults (≥18 years), and mixed age populations. Further RCT charac-teristics were assessed using information registered in the database: study location, funding source, year of reg-istration, study phase, study design, type of intervention evaluated, blinding procedure, study duration, and enroll-ment achieved. A logistic regression model was applied to assess the impact of participant’s age category on trial completion while controlling for other potentially rele-vant trial characteristics.
Results A total of 65 095 registered RCTs matched eligi-bility criteria. Paediatric and mixed age trials represented respectively 6.6% (n=4,314) and 8.9% (n=5,806) of regis-tered RCTs, and these proportions remained unchanged over the years. Among paediatric trials, 2151 were com-pleted (49.9%) and 367 were discontinued (8.5%). In adult and mixed age RCTs respectively, 27 338 (49.7%) and 2782 (47.9%) were completed, whereas 5584 (10.2%) and 546 (9.4%) were discontinued. Overall, paediatric and mixed age RCTs were more likely to be registered as com-pleted than adult RCTs (OR: 1.16, CI95%: 1.02–1.30; OR: 1.15, CI95%: 1.04–1.27, respectively). Also, RCTs were more likely to be registered as completed when they evaluat-ed interventions other than drugs/biologicals or devices/procedures, when the primary trial purpose was to eval-uate a non-therapeutical intervention, when they were funded by industry, when they were designed as cross-over trials, and when they included a masking procedure.
Conclusion Paediatric or mixed age RCTs are more likely to be registered as completed than RCTs in adults. Con-trary to current perceptions and despite the specific chal-lenges of paediatric research, recruitment of children and adolescents is not a limiting factor to completing a RCT. Other study features, such as funding and design, impact completeness and should be carefully considered before initiating clinical research.
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