The statistical significance of randomized controlled trial results is frequently fragile: a case for a Fragility Index.
Walsh Michael, Srinathan Sadeesh K, McAuley Daniel F, Mrkobrada Marko, Levine Oren, Ribic Christine, Molnar Amber O, Dattani Neil D, Burke Andrew, Guyatt Gordon, Thabane Lehana, Walter Stephen D, Pogue Janice, Devereaux P J
Journal of clinical epidemiology · 2014 · PMID 24508144 · 인용 755
OBJECTIVES: A P-value <0.05 is one metric used to evaluate the results of a randomized controlled trial (RCT). We wondered how often statistically significant results in RCTs may be lost with small changes in the numbers of outcomes. STUDY DESIGN AND
SETTING: A review of RCTs in high-impact medical journals that reported a statistically significant result for at least one dichotomous or time-to-event outcome in the abstract. In the group with the smallest number of events, we changed the status of patients without an event to an event until the P-value exceeded 0.05. We labeled this number the Fragility Index; smaller numbers indicated a more fragile result.
RESULTS: The 399 eligible trials had a median sample size of 682 patients (range: 15-112,604) and a median of 112 events (range: 8-5,142); 53% reported a P-value <0.01. The median Fragility Index was 8 (range: 0-109); 25% had a Fragility Index of 3 or less. In 53% of trials, the Fragility Index was less than the number of patients lost to follow-up.
CONCLUSION: The statistically significant results of many RCTs hinge on small numbers of events. The Fragility Index complements the P-value and helps identify less robust results.