New clinical trials in primary biliary cirrhosis: design and endpoints

During the last 30 years, clinical trial methodology has evolved from the interface of epidemiology, biostatistics, and clinical medicine to a specialty with its own experts, terminology, computer programs, books, and journals. During much of this time, randomized clinical trials for the treatment of primary biliary cirrhosis (PBC) were being conducted1–5. This chapter discusses three important issues in the design of therapeutic trials of PBC: choice of the primary research issue, sample size and power calculations, and choice of the primary response variable. It is hoped that consideration of these issues will result in well-planned trials in PBC and will serve a note of caution to investigators before embarking on a trial that may not be capable of achieving its goal.