Zsa Zsa Weerts

Chapter 2 36 Information on demographics was collected using a predefined self-report questionnaire. Furthermore, subjects completed the gastrointestinal symptom rating scale (GSRS) 18 , hospital anxiety and depression scale (HADS) 19,20 and rand 36-item short-form health survey (SF-36) 21,22 for GI symptom severity, co-occurrence of depressive and/or anxiety symptoms and general quality of life, respectively. In addition, in a subset of participants a rectal barostat procedure was performed. Measurement of rectal perception was performed using a standardized perception protocol, during which 17 pressure steps between 0 and 50 mm Hg, based on a semi- random staircase protocol, were applied. During each pressure step pain scores were reported on a 100 mm visual analogue scale (VAS). The cut-off value for visceral hypersensitivity was defined as a pain score ≥20 at pressure ≤26 mm Hg. A detailed description on the rectal barostat procedure was previously reported. 23 The end-of-day diary data were additionally used to perform an exploratory analysis on whether Rome III IBS patients, that do not fulfill (surrogate) Rome IV criteria for IBS, are likely to fulfill Rome IV criteria for other functional bowel disorders. Definitions that were used for retrospective evaluation of Rome IV diagnoses for functional constipation (FC), functional diarrhea (FD) and functional abdominal bloating/distension (FAB/D) are shown in Table S2.1 . Since the symptom diary was designed for IBS and not specifically for assessing those other disorders, not all criteria could be definitively checked. Data and statistical analyses All analyses were performed using IBM SPSS Statistics, version 23 (IBM Statistics for Macintosh, Chicago, IL, USA). The total study population is referred to as ‘total’. Depending on whether subgroups are highly likely to fulfill Rome IV criteria based on the end-of-day diary or not they are referred to as ‘Rome IV-positive’ and ‘Rome IV-negative‘, respectively. Results for ‘Rome IV-positive’ and ‘Rome IV-negative‘ are presented separately for both definitions of fulfilling Rome IV criteria: ‘Definition 1: Abdominal pain score ≥2 once a week in each week’ and ‘Definition 2: Abdominal pain score ≥3 once a week in each week’. Categorical data are presented as proportions and differences between groups are tested using 2 or Fisher’s exact test. Continuous data are presented as medians and interquartile ranges (IQR) and groups are compared using Mann-Whitney U test, taking