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Non-Inferiority and Superiority Trials
The objective of non-inferiority trials is to compare a novel treatment to an active treatment with a view of demonstrating that it is not clinically worse with regards to a specified endpoint. It is assumed that the comparator treatment has been established to have a significant clinical effect (against placebo).
These trials are frequently used in situations where use of a superiority trial against a placebo control may be considered unethical.
Non-inferiority is most easily assessed using a confidence interval (CI) approach.
Firstly the trial investigators specify a non-inferiority margin, delta. This is the maximum difference that they are prepared to tolerate in a given direction if the new treatment is not to be considered (clinically) inferior.
If a 95% confidence interval for the difference between treatment means lies above or below this boundary value (in a favourable direction) then non-inferiority is deemed to have been established.
Logic of Non-Inferiority studies
Setting the non-inferiority margin
Interpreting a noninferiority trial as a superiority trial
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