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IBS symptoms and quality of life 53 3 performed to exclude organic diseases. A history of abdominal surgery automatically led to exclusion, except for an uncomplicated appendectomy, hysterectomy, or cholecystectomy. Data collection At time of enrollment in the MIBS Cohort, patients completed several questionnaires, i.e. on demographics and lifestyle, GI symptoms, symptoms of comorbid anxiety and depression, and general quality of life. The data were obtained administering a predefined self-report questionnaire on demographics and lifestyle, an end-of-day 14 days symptom diary, the gastrointestinal symptom rating scale (GSRS, scale 1-7, generates symptom scores for the following subdomains: abdominal pain, reflux, diarrhea, constipation, indigestion) 19 , the hospital anxiety and depression scale (HADS, scale 0-3, a screening tool for anxiety and depression) 20,21 , and the rand 36-item short- form health survey (SF-36, scale 1-6, generates a physical and a mental quality of life component summary). 22,23 Approximately five years (+/- two years) after inclusion, patients were invited to complete several follow-up questionnaires. These included the same questionnaires that were filled out at baseline (with the exception of the end-of-day diary), with the addition of other questionnaires to further standardize the phenotyping of our population and to allow valid comparisons to other cohorts ( i.e. international harmonization). Additional questionnaires included: the GSRS specific for IBS (GSRS-IBS, scale 1-7, generates symptom scores for the following subdomains: abdominal pain, bloating, constipation, diarrhea, satiety) 24 ; the Visceral Sensitivity Index (VSI, scale 1-6, assesses GI-specific anxiety or, in other words, fear for GI symptoms) 25 ; and the Satisfaction With Life Scale (SWLS, scale 1-6, assesses individual overall satisfaction with life). 26-28 As it is known that IBS can affect the ability to work 29 , a self-report questionnaire regarding productivity (Productivity Cost Questionnaire (PCQ), validated for the Dutch situation) was included as well. 30,31 Patients could opt for paper or digital web-based (invitation was sent via email) questionnaires to encourage participation. One reminder was sent when no response had been received within one month. A trained clinical investigator contacted all patients who did respond and confirmed the Rome III diagnostic criteria during a telephonic interview with them. Patients were reassigned IBS subtypes based on their predominant bowel habit, during the follow-up measurement. Reliable information on treatment history was not available for the majority of patients as this was not registered systematically during the follow-up period. Furthermore, many patients underwent self-treatment or treatment via their primary care physician, of