Abstract

In the classical randomized controlled trial (RCT) the aim is to show that one treatment is superior to another. This is called the superiority trial. However, nowadays it often occurs that the experimental treatment is not expected to show a better efficacy, but rather aims to improve upon the current treatments in other aspects, e.g. better safety profile, easier to administer, cheaper, etc. In that case, we may wish to show that the experimental and the control treatment do not differ in efficacy but that the experimental treatment has some other advantages. A non-significant outcome of a superiority trial is, however, not a proof of equal efficacy performance. In contrast, we need to set up another clinical trial design, called the non-inferiority (NI) trial. In that case, one needs to specify upfront what is meant by “equality of efficacy”, and the practical and statistical aspects of the trial may be quite different from a superiority trial.

In this presentation the non-inferiority trial is contrasted to the superiority trial. Practical aspects and pitfalls when setting-up a NI trial and/or interpreting the results of a NI trial will be discussed. It is shown that NI trials pose different, and often more complex, practical problems than superiority trials. Practical recommendations for setting up a NI trial are given.