Assessing the fragility index of randomized controlled trials on carotid artery stenosis: a systematic review

The fragility index (FI) measures the robustness of randomized controlled trials (RCTs) with dichotomous outcomes, calculated as the number of patients whose outcome would need to change for a significant result to become non-significant. Many RCTs have compared carotid endarterectomy (CEA) and carotid artery stenting (CAS), with variable results; thus, in this systematic review, we sought to explore the FI as a possible explanation for the variability in trial results between CEA and CAS.

We conducted a search in MEDLINE (1946 to Apr. 22, 2024), Embase (1974 to Apr. 22, 2024), and PubMed (up to Apr. 22, 2024) for RCTs comparing CEA and CAS. We included RCTs with statistically significant results and dichotomous primary outcomes.

Our literature search identified 11 RCTs involving 5296 patients (n = 2640 CEA, n = 2656 CAS). All studies except 1 favoured CEA, with the exception favouring CAS. The median FI was 11 (interquartile range 2 to 22). Interestingly, 100% of the studies had loss to follow-up (LTFU) greater than its FI.

A small number of events is required to change the findings of RCTs comparing CEA to CAS from statistically significant to statistically nonsignificant. All studies that reported LTFU had LTFU greater than its FI, calling into question the robustness of these results.