To the Editor Acuna et al1 claim that, unlike a superiority study, interpretation of noninferiority studies is not straightforward, ie, the result from a noninferiority trial should be classified as noninferior, inconclusive, or not noninferior, but the result from a superiority trial is positive or negative. We respectfully disagree with this statement. In fact, one can design and analyze a study via 95% confidence intervals without prespecifying a superiority or inferiority hypothesis. That is, at the design stage, one may define a prespecified confidence interval width (eg, 10% for a study assessing laparoscopy for surgical resection1) as the required precision for estimating between-group difference and calculate the sample size accordingly. This width can be chosen from clinical considerations and/or feasibility of conducting the study. At the analysis stage, one then uses the observed confidence interval to claim superiority, noninferiority, inconclusive results, or inferiority for the new treatment, depending on where this interval is located, eg, items 1, 3, 5, and 8, respectively, in Figure, A.1 We claim that item 5 is inconclusive, since its confidence interval is very large, indicating insufficient information for decision making. On the other hand, the confidence interval for item 3 is sufficiently narrow for claiming noninferiority or equivalence. This unified approach seems more appealing than that under either the superiority or noninferiority trial hypothesis testing setting.
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Claggett B, Uno H, Wei L. Unifying Design and Analysis for Superiority and Noninferiority Trials With Appropriate End Point. JAMA Surg. 2019;154(5):466–467. doi:10.1001/jamasurg.2018.5852
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