2.3.5. The Visual Analog Scale for Irritable Bowel Syndrome Questionnaire

The VAS-IBS is a validated symptom-assessment questionnaire [24] covering abdominal pain, diarrhea, constipation, bloating and flatulence, vomiting and nausea, psychological well-being, and intestinal symptoms’ influence on daily life. Items are measured on a scale of 0–100 mm, ranging from absent (0 mm) to very severe (100 mm) symptoms. The values are inverted from the original format, where 100 mm indicated ‘no symptoms’. Reference values of VAS-IBS in a healthy population were previously determined by a control material consisting of 90 healthy volunteers (median age: 44 [range, 21–77] years, 57% women) included from staff at the Skåne University Hospital, Department of Internal Medicine, during 2010 [25].

Participants in the MOS could not be used as controls for VAS-IBS variables as they were instructed not to complete the VAS-IBS questionnaire if they negated presence of GI symptoms during the past 2 weeks.