Objective: Poor descriptions of standard care may compromise interpretation of results in randomised controlled trials (RCTs) of health interventions. We investigated quality of standard care in RCTs of behaviour change interventions for young people with type 1 diabetes and consider implications for evaluating trial outcomes.
Design: We conducted systematic searches for articles published between 1999 and 2012. We extracted standard care descriptions and contacted trial authors to complete a checklist of standard care activities. The relationship between standard care quality and outcomes was examined via subgroup meta-analyses and meta-regression.
Main outcome measures: Standard care descriptions, standard care quality, and relationships between standard care quality with medical and psychological outcomes.
Results: We identified 20 RCTs described across 26 articles. Published descriptions of standard care were limited to service-level features. Author responses indicated standard care provision extended beyond published accounts. Subgroup analyses suggested control groups receiving higher standard care quality showed larger improvements in both medical and psychological outcomes, although standard care quality did not predict outcomes significantly.
Conclusion: The quality of care delivered to control group participants can influence outcomes of RCTs. Inadequate reporting exacerbates this issue by masking variations between trials. We argue for increased clarity in reporting standard care in future trials.
Keywords: control group; meta-analysis; reporting; standard care quality; type 1 diabetes.