Crossover: Design, measures, and classic example

Crossover trials enable subjects to receive all the treatments of interest in a randomized sequence, thus allowing for each subject to act as their own control. This can reduce the number of subjects needed to adequately power a study, but investigators must account for potential carry-over effects and ensure that sufficient washout periods are incorporated in these studies. Cross-over trials work best in studying chronic diseases. This chapter provides classic examples within the field of gastroenterology to display the benefits and limitations of this study design.