The fragility index in randomized clinical trials supporting clinical practice guidelines for acute coronary...

In randomized clinical trials (RCTs) rejecting the null hypothesis, the fragility index (FI) yields the minimum number of participants who would need to have had a different outcome for the results of the trial to become non-significant. We evaluated the robustness of RCTs supporting American College of Cardiology/American Heart Association (ACC/AHA) and European Society of Cardiology (ESC) clinical practice guidelines (CPGs) for ST-elevation myocardial infarction (STEMI) and non-ST-elevation acute coronary syndrome (NSTE-ACS) using the FI.

There were 407 RCTs among the 2128 studies cited in the 2013 and 2014 ACC/AHA and 2017 and 2020 ESC CPGs for STEMI and NSTE-ACS, respectively. The FI could be calculated in 132 RCTs (32.4%) meeting the needed criteria for its estimation (two-arm RCT, 1:1 allocation, binary outcome, P < 0.05). The median FI was 12 (interquartile range: 4-29). Hence, a change in the outcome status of 12 patients would be needed to reverse the statistical significance of the primary endpoint in 50% of the RCTs. The FI was ≤1% than their sample size in 55.7% RCTs, whereas in 47% of RCTs, the FI was lower than the number of patients lost to follow-up. Some study design features were associated with a higher FI (international, multicentre, private funding; all P < 0.05), whilst baseline patient characteristics were not substantially different by FI (e.g. age, female sex, white study participants; all P > 0.05), except for geographic enrolment (P = 0.042).

The FI might be useful to evaluate the robustness of those RCTs with statistically significant findings for the primary endpoint that have an impact on key guideline recommendations.