The fragility of statistically significant results in otolaryngology randomized trials

Mason Skinner, Daniel Tritz, Clayton Farahani, Andrew Ross, Tom Hamilton, Matt Vassar
American Journal of Otolaryngology 2018 October 22

OBJECTIVES: The American Academy of Otolaryngology-Head and Neck Surgery regards randomized controlled trials as class A evidence. A novel method to determine the robustness of outcomes in trials is the fragility index. This index represents the number of patients whose status would have to change from a non-event to an event to make a statistically significant result non-significant.

METHODS: Investigators included otolaryngology journals listed in the top 10 of one or both of Google Scholar Metrics and Clarivate Analytics' Journal rankings. For inclusion, a randomized controlled trial needed to report a one-to-one random assignment of participants to condition, contain two parallel arms or have used a two-by-two factorial design, and report at least one statistically significant dichotomous outcome.

RESULTS: Sixty-nine trials met inclusion criteria. The median fragility index was three events (interquartile range 1-7.5). Median sample size was 72 (interquartile range 50-102.5). Modest correlations were observed between fragility index and total sample size (r = 0.27) and fragility index and event rate (r = 0.46). Investigators found no correlation between fragility index and impact factor or Science Citation Index. In 39% (27/69) of trials, the number lost to follow-up was equal to or greater than the fragility index.

CONCLUSION: A median fragility index of 3 indicates that three people, on average, are needed to alter the outcomes in otolaryngology trials. This indicates that the results of two-group randomized controlled trials reporting binary endpoints published in otolaryngology journals may frequently be fragile.


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