A generalized concept of power helped to choose optimal endpoints in clinical trials

Objectives: A clinical trial may have multiple objectives. Sometimes the results for several parameters may need to be significant or meet certain other criteria. In such cases, it is important to evaluate the probability that all these objectives will be met, rather than the probability that each will be met. The purpose of this article is to introduce a definition of power that is tailored to handle this situation and that is helpful for the design of such trials. Study Design and Setting: We introduce a generalized concept of power. It can handle complex situations, for example, in which there is a logical combination of partial objectives. These may be formulated not only in terms of statistical tests and of confidence intervals, but also in nonstatistical terms, such as "selecting the optimal by dose." Results: The power of a trial was calculated for various objectives and combinations of objectives. Conclusion: The generalized concept of power may lead to power calculations that closely match the objectives of the trial and contribute to choosing more efficient endpoints and designs. (C) 2007 Elsevier Inc. All rights reserved.