Govert Veldhuijzen

91 CBE is non-inferior to nurse counselling prior to colonoscopy, a multicenter RCT Inventory (STAI). This commonly used 20-item self-report instrument provides scores ranging from 20 (absence of anxiety) to 80 (high anxiety) combining both State (dynamic, at one particular moment) and Trait (static, based on character) anxiety levels. 15 Patients reported sickness absence leave at T2, with the adapted iMTA Productivity Cost Questionnaire to evaluate the macroeconomic effect. (Appendix 2s.) 16 Information re-call was tested at T2 using the same 10-item information re-call test used in our prior pilot study. 11 For patient satisfaction, two measures were recorded at T3. First, the patients were asked about their willingness to return to the endoscopy unit. This is commonly used in the context of patient satisfaction in endoscopy. 20 Next, the Net Promoter Score (NPS) is utilized on the question “Would you recommend this endoscopy unit to your peers?”. Patient’s scores range from 1 (Not at all likely) to 10 (Extremely likely). The NPS is calculated as % Promoters (scores 9-10) - % Detractors (scores 1-6). 18 Statistical analysis Data was analysed on an intention-to-treat and per-protocol basis. Presentation of the data included the means, medians and standard deviations for quantitative data. The point estimates are presented with 95% confidence intervals (CI).” In case of categorical data, counts and frequencies were used. We used the relative risk of an inadequately prepared colon to compare both groups. In comparable bowel preparation studies, 90% success rate (for an adequately prepared colon) is commonly used, with a 10% non-inferiority margin as the maximum clinically acceptable difference. 19,21 The non-inferiority power calculation resulted in 180 patients per group, 360 patients in total. With a margin of ± 60% attrition of patients before completing the protocol, based on earlier research, the target number of patients to approach was set at 1,000 to acquire the adequate per-protocol sample. Comparisons between groups were assessed using bi-variate analyses. In addition to the non-inferiority analyses in the intention-to-treat and per-protocol population, superiority analyses (Chi-Square, t-test, ANCOVA) were conducted to investigate effects on secondary outcome measures. Possible differences between the groups concerning secondary outcomes were assessed using two-sided testing. P-values <0.05 were considered statistically significant for the secondary outcomes and no correction for multiple testing was performed as these analyses were considered exploratory. 5