Using Prior Findings to Augment Active-Controlled Trials and Trials with Small Placebo Groups

Abstract

Procedures are presented for incorporating external information into inferences about outcomes from clinical and other trials. The objective is to use findings from trials that did include placebo to construct predictive distributions for evaluating the likelihood of a significant active-placebo difference in active-controlled trials that include no or few placebo controls. Information about differences between active controls and placebo from other trials also can be incorporated. The predictive distributions allow for random between-study variation in the variances as well as in the means. The calculations are summarized with simple graphical displays.