Guideline Evidence Audits Require Robustness Beyond the Fragility Index

Abstract

Fragility index audits of clinical guideline evidence measure classification stability but not distance from therapeutic neutrality — leaving the most consequential question in evidence grading unanswered. Applied to the randomized controlled trials recently cited in the NCCN guidelines for gastric cancer, the fragility index cannot distinguish a low-powered detection of a real treatment effect from a near-null result that narrowly crossed the significance threshold, a distinction with direct implications for confirmatory trial prioritization and guideline strength ratings. The significance-fragility-robustness framework resolves this gap by adding robustness dimension — a geometrically derived, model-free measure of distance from therapeutic neutrality — as an orthogonal third statistical metric alongside significance and fragility, completing the evidence picture that guideline audits require.