An overview of group sequential methods in longitudinal clinical trials

During the last decade, several papers have been published on group sequent ial methods in general and on sequential longitudinal clinical trials in pa rticular. This paper gives an overview of the proposed methods, emphasizing longitudinal clinical trials. Furthermore, it tries to answer some practic al questions that may arise during the conduct of interim analyses in longi tudinal trials. Simulations have been carried out to obtain insight in thes e practical considerations.