Interpretation of CIs in clinical trials with non-significant results: systematic review and recommendations

OBJECTIVES: Interpretation of CIs in randomised clinical trials (RCTs) with treatment effects that are not statistically significant can distinguish between results that are ‘negative’ (the data are not consistent with a clinically meaningful treatment effect) or ‘inconclusive’ (the data remain consistent with the possibility of a clinically meaningful treatment effect). This interpretation is important to ensure that potentially beneficial treatments are not prematurely abandoned in future research or clinical practice based on invalid conclusions. DESIGN: Systematic review of RCT reports published in 2014 in Annals of Internal Medicine, New England Journal of Medicine, JAMA, JAMA Internal Medicine and The Lancet (n=247). RESULTS: 85 of 99 articles with statistically non-significant results reported CIs for the treatment effect. Only 17 of those 99 articles interpreted the CI. Of the 22 articles in which CIs indicated an inconclusive result, only four acknowledged that the study could not rule out a clinically meaningful treatment effect. CONCLUSIONS: Interpretation of CIs is important but occurs infrequently in study reports of trials with treatment effects that are not statistically significant. Increased author interpretation of CIs could improve application of RCT results. Reporting recommendations are provided.