Zsa Zsa Weerts

Rome III versus Rome IV criteria for IBS 35 2 February 2009 and was executed according to the revised Declaration of Helsinki (64 th WMA General Assembly, Fortaleza, Brazil, October 2013). Furthermore, the study has been registered in the US National Library of Medicine ( http://www.clinicaltrials.gov, NCT00775060). Study participants Between July 2009 and May 2016, IBS patients aged 18-75 years were included in the Maastricht IBS cohort at the secondary/tertiary care outpatient department of Gastroenterology-Hepatology at the Maastricht UMC+ in Maastricht and via general practitioners practices in South-Limburg, the Netherlands. All subjects fulfilled the Rome III criteria (see Box 2.1 ) for IBS and were assigned the IBS subtype based on predominant bowel habit, i.e. diarrhea (IBS-D), constipation (IBS-C), a mix of diarrhea and constipation (IBS-M) or unspecified predominant bowel habit (IBS-U). 3,17 Rome III criteria were evaluated in a face-to-face interview by a trained clinical researcher. Medical history was taken by a gastroenterologist and if indicated, GI endoscopy, abdominal imaging and/or blood, breath or fecal analyses were performed to exclude organic disease. A history of abdominal surgery, except for uncomplicated appendectomy, cholecystectomy or hysterectomy, was reason for exclusion. All subjects gave their written informed consent before participation. Data collection As subject inclusion was performed since 2009, Rome IV criteria were not collected in a face-to-face interview at the moment of inclusion. However, all participants completed an end-of-day diary on symptom severity and bowel habits, during 14 days, at the time of inclusion. Abdominal pain, amongst other symptoms, was scored using a 5-point Likert scale (1=not at all; 2=mild; 3=considerable; 4=severe; 5=extremely). Using this information, we retrospectively determined which subjects were highly likely to fulfill the Rome IV criteria, based on the presence of abdominal pain on at least one day in both the first and the second seven days ( i.e. abdominal pain at least once a week). Rome IV criteria do not take into account abdominal pain severity, however, as we will use surrogate Rome IV criteria to evaluate differences between Rome IV-positive and - negative IBS patients, we will report on two definitions for those 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’. Only symptom diaries that were completed for at least 12 of the 14 days were considered eligible for analysis.