Truncated group sequential test for clinical trials

Abstract

Although a sequential test, in general, requires a smaller sample size on the average, most clinical trials are not designed in a sequential approach. One of the reasons is that the sample size by a sequential test can exceed that required by an equivalent fixed-sample size test. Truncation of a triangular sequential design is considered in this paper. It is intended so that the maximum sample size for the test becomes approximately equal to the sample size for the fixed-sample test of about the same power. The method is intended for one-sided group sequential tests where the treatment group is compared to the control group for the difference in proportions. The method is illustrated using a clinical trial of head injury patients. Comparisons with other group sequential tests suggested that the proposed method may provide a more efficient test in clinical trials.