2604.01157 The Concordance Fragility Index: How Many Patient Exclusions Reverse the Conclusion of a Survival Analysis?
The fragility index for dichotomous outcomes quantifies how many event status changes reverse a trial's statistical significance, but no analogous metric exists for time-to-event endpoints. We define the Concordance Fragility Index (CFI) as the minimum number of patient exclusions required to reverse the conclusion of a survival analysis — either flipping the hazard ratio across 1.