Principles of sample size calculation in gastroenterology research: a practical guide for clinicians.

A proper sample size calculation enables to conduct adequately powered randomized controlled trials (RCTs) and to provide a valid assessment of a specific clinical question. In the current manuscript we tried to provide the reader with an easy guide on the principles of sample size calculation in RCTs, tailored specifically to the context of gastroenterology and hepatology. The basics of sample size calculation were commented with a description of some of the main methods, including the calculation of the non-inferiority margin for non-inferiority RCTs and the calculation of the minimum clinically important difference (MCID). Some examples from the gastroenterology literature were also provided. Collaborating with a biostatistician can provide valuable insights into the nuances of sample size calculation and study design. However, it is crucial that the clinicians understand the basics of calculating sample size so they could provide valuable input in designing the study from clinical point of view.