Group sequential testing in clinical trials with multivariate observations: a review

Most group sequential testing procedures assume that each patient has only one response. Thus interim test statistics have independent increments. In many clinical trials, however, a response variable is measured at each follow-up visit. In this article, I review some recently developed group sequential methods for repeated measures and for other types of multivariate responses. Six parametric methods and three non-parametric methods are included. My review focuses on the comparison of the assumptions made and the applications of each of these methods.