Optimization of testing times and critical values in sequential equivalence testing

Abstract

In long-term clinical trials, interim analyses are planned to reduce the number of patients needed. To meet this issue in a practical way, group sequential designs are used. Most of these trials are conducted with the objective of demonstrating differences in efficacy of treatments, for example, to show superiority of a new drug or experimental treatment to a control. However, an increasing number of trials are designed to establish equivalence in efficacy or bioequivalence. This paper deals with group sequential test procedures in two-sided equivalence trials. Optimized designs with respect to sample size behaviour are constructed. Tables containing optimal testing times and corresponding optimal critical values or values to construct an underlying alpha-spending function, respectively, are provided. An example illustrates their use when planning interim analyses in equivalence trials.