Sample size determination in clinical trials with multiple co-primary endpoints including mixed continuous and binary variables

Regarding Paper Sample size determination in clinical trials with multiple co-primary endpoints including mixed continuous and binary variables by T. Sozu, T. Sugimoto, and T. HamasakiBiometrical Journal (2012) 54(5): 716-729 Article: http://dx.doi.org/10.1002/bimj.201100221 Authors' Reply: http://dx.doi.org/10.1002/bimj.201300032 This paper recently introduced a methodology for calculating the sample size in clinical trials with multiple mixed binary and continuous co-primary endpoints modeled by the so-called conditional grouped continuous model (CGCM). The purpose of this note is to clarify certain aspects of the methodology and propose an alternative approach based on latent means tests for the binary endpoints. We demonstrate that our approach is more powerful, yielding smaller sample sizes at powers comparable to those used in the paper.