A one-sided interim analysis with binary outcomes.

Abstract

Wieand and Therneau (Controlled Clin Trials 8:20-28, 1987) proposed a technique for conducting a clinical trial to test the equality of response rates for two treatments using a one-sided test with an option of terminating the trial at the single interim analysis if it appears that the test treatment will offer no improvement over the control treatment. Chi, Bristol, and Castellana (Stat Med 5:387-392, 1986) considered a clinical trial with the same option when the treatments are compared with respect to the means of variables with normal distributions with a common known variance. Here a decision rule similar to the one proposed in the latter is employed for the problem examined in the former. This decision rule, a generalization of the one proposed by Wieand and Therneau, consists of a one-sided test at the final analysis with a one-sided test at the interim analysis, which is performed in the direction opposite to the one at the final analysis. It is shown that the proposed generalization may result in desirable properties regarding the probability of stopping the trial at the interim analysis in some situations.