Why is everyone talking about non inferiority trials? Learn about non inferiority trials like a pro clinical trialist. Most of the time, clinical trials look to determine if treatment A is better than treatment B. These are called superiority trials. Every clinical trial creates a point estimate, or best guess, as well as a confidence interval, a span within which the data suggests the true effect is likely to exist.

In order to demonstrate with certainty that treatment A is better than treatment B. The confidence interval must not include the null hypothesis, that is, that treatment A is equal to treatment B. But we’re not always interested in knowing whether treatment A is better than treatment B, and sometimes we might be able to accept an alternative if we know it’s not much worse. In other words, the treatment is non inferior to the standard. β€ŠIn this kind of trial, we look to see whether the confidence interval overlaps the chosen non inferiority margin. The margin chosen by the trialist should be a clinically significant difference beyond which the new treatment would be unacceptable.

Let’s take a look at some non inferiority trial results and try to interpret them.

Values on the right side of the line indicate the control is better, whereas values on the left side of the line indicate the new treatment is better. So this is the same graph we saw before looking at superiority, and you can tell because the lower bound of the confidence interval is above both the null and the non inferiority margin.

This confidence interval overlaps the null, but doesn’t overlap the non inferiority margin, demonstrating non inferiority. Whereas this one does overlap the non inferiority margin, making it not non inferior. Here the entire confidence interval is below the null, making the new treatment inferior to the standard of care.

Why do we perform non inferiority trials? There are three main reasons. 1. If there’s an accepted standard of care treatment, it may be unethical to perform a placebo controlled trial. β€Š2. It can be cheaper to perform a smaller non inferiority trial. β€Š3. And most commonly, the new treatment has other benefits, such as cost or convenience, that aren’t captured in the primary outcome, such as comparing a new oral medication to a standard of care IV.

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Non-Inferiority Trial

Non-Inferiority Trial: Part 2

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