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October 27, 2004

Tenofovir, Equivalence, and Noninferiority—Reply

Author Affiliations

Letters Section Editor: Robert M. Golub, MD, Senior Editor.

JAMA. 2004;292(16):1951-1952. doi:10.1001/jama.292.16.1951-b

In Reply: Although the terms “equivalence” and “noninferiority” are not strictly the same, we did use them interchangeably, as is commonly done.1 This study was designed as a noninferiority study with a prespecified noninferiority margin of 10% chosen as in the “Methods” section.

The 2-sided 95% CI of the difference between 2 trial arms is an appropriate and traditional method for assessing equivalence of 2 treatments.1,2 The same procedure is often advocated for assessing noninferiority of a new drug (or regimen) compared with a reference drug,1 even though in noninferiority studies emphasis is on the lower bound of the 95% CI. Indeed, the use of a 2-sided 95% CI (equivalent to a 1-sided 97.5% CI) is advocated by US and European regulatory agencies36 for noninferiority studies. While academic statisticians often use 1-sided 95% CIs to assess noninferiority, we chose the more conservative 2-sided approach, as suggested by these regulatory authorities.

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