The Intestinal Gas Questionnaire (IGQ): Psychometric validation of a new instrument for measuring gas-related symptoms and their impact on daily life among general population and irritable bowel syndrome.

BACKGROUND Gas-related symptoms (GRS) are common in the general population (GPop) and among patients with disorders of gut-brain interactions but there is no patient-reported outcome evaluating these symptoms and their impact on daily life. We have previously developed a 43-item intestinal gas questionnaire (IGQ). The aim of the present study is to perform a psychometric validation of this instrument. METHODS Participants (119 from the GPop and 186 irritable bowel syndrome (IBS) patients) were recruited from 3 countries (UK, Spain, France). IBS patients fulfilled ROME IV criteria with an IBS severity score between 150 and 300. Participants completed the IGQ, the functional Digestive Disorders Quality of Life (FDDQL), and the EQ-5D. A subgroup (n = 90) repeated the IGQ completion after 7 days on paper or electronically. RESULTS From the original IGQ questionnaire, 26 items were deleted because of poor performance. Confirmatory factorial analysis on the remaining 17 items (7 symptom and 10 impact items) yielded a 6-factor structure accounting for 67% of the variance for bloating (6 items), flatulence (3), belching (2), bad breath (2), stomach rumbling (2), and difficult gas evacuation (2). Global score (0-100) was worse among IBS vs GPop (40 ± 15 vs 33 ± 17; p = 0.0016). At the second visit, the intraclass correlation coefficient of IGQ scores was between 0.71 and 0.86 (n = 67) for test-retest reliability and 0.61-0.87 (n = 64) for equivalence between electronic and paper versions of IGQ. CONCLUSION The IGQ available in paper and electronic versions in 3 languages is a robust instrument for capturing and measuring GRS and their impact on daily life.