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Non-inferiority trials: Why, what and how?

Authors: Mara Therese P. Evangelista, MD and Nicholas Earl Huber


Most clinical trials are designed to show that a new intervention is superior to an existing intervention (or to no intervention, if none is currently available). These designs are called superiority trials. However, sometimes a new intervention is not expected to be clinically superior to an existing product, but has other advantages, (i.e. being cheaper, easier to administer, or has a better safety profile).

To conclude that the clinical efficacy of new intervention is “at least as good” as the current intervention, one should use a non-inferiority trial design. Establishing non-inferiority means that the clinical efficacy of the experimental intervention is, at worst, only marginally inferior to that of the existing intervention. This margin of clinical unimportance is pre-defined prior to study commencement.

To understand the concepts of non-inferiority trials and how they differ from superiority trials.

• Define non-inferiority
• Explain why non-inferiority trials are conducted
• Give concrete examples when a non-inferiority trial should be used
• State the principles for defining eligibility and treatment selection in non-inferiority trials
• Expound on the need for rigorous design and conduct of non-inferiority trials
• Clarify the need for both intention to treat and per protocol analyses for non-inferiority trials
• Descibe how to use the results of a non-inferiority trial, in particular the confidence interval for the primary endpoint, in deciding whether non-inferiority has been shown



Evangelista, MT & Huber, NE. (2017) Non-inferiority trials: Why, what and how?. Journal of the Philippine Dermatological Society, 26(1), 8-11.



non-inferiority trial, epidemiology, trial


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Non-inferiority trials: Why, what and how?