<qa>  What was the main outcome of the colonoscopy?Adults referred for colonoscopy were included in a Dutch large volume endoscopy unit. Exclusion criteria were illiteracy in Dutch and audiovisual handicaps. Patients were prospectively divided into two groups, one receiving nurse counselling and one receiving CAI and a nurse contact before colonoscopy. The main outcome, cleanliness of the colon during examination, was measured with the Ottawa Bowel Preparation Scale OBPS and the Boston Bowel Preparation Scale BBPS. Patient comfort and anxiety were assessed at multiple time points: directly after the instruction and one hour before colonoscopy. Comfort was rescored 2 hours after colonoscopy. We also tested knowledge and comprehension one hour before colonoscopy. Statistical analyses included Mann-Whitney. 