Meta-analysis of cardiovascular superiority trials published in the New England Journal of Medicine to elucidate the concept of superiority margin.

OBJECTIVE: To show that overpowered trials claim statistical significance detouring clinical relevance and warrant the need of superiority margin to avoid such misinterpretation. DESIGN: Selective review of articles published in the New England Journal of Medicine between 1 January 2015 and 31 December 2018 and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. ELIGIBILITY CRITERIA FOR SELECTING STUDIES AND METHODS: Published superiority trials evaluating cardiovascular diseases and diabetes mellitus with positive efficacy outcome were eligible. Fixed effects meta-analysis was performed using RevMan V.5.3 to calculate overall effect estimate, pooled HR and it was compared with mean clinically significant difference. RESULTS: Thirteen eligible trials with 164 721 participants provided the quantitative data for this review. Largely, the primary efficacy endpoint in these trials was the composite of cardiovascular death, non-fatal myocardial infarction, unstable angina requiring rehospitalisation, coronary revascularisation and fatal or non-fatal stroke. The pooled HR was 0.86 (95% CI 0.84 to 0.89, I2=45%) which was lower than the mean clinically significant difference of 0.196 (19.6%, range: 0.09375-0.35) of these studies. There was a wide 95% CI in these studies from 0.56 to 0.99. The upper margin of CI in most of the studies was close to the line of no difference. Absolute risk reduction was small (1.19% to 2.3%) translating to a high median number needed to treat of 63 (range: 43 to 84) over a follow-up duration of 2.95 years. CONCLUSIONS: The results of this meta-analysis indicate that overpowered trials give statistically significant results undermining clinical relevance. To avoid such misuse of current statistical tools, there is a need to derive superiority margin. We hope to generate debate on considering clinically significant difference, used to calculate sample size, as superiority margin.