Background: Gas-related symptoms (GRS) are common among the general population (GP° and patients with functional gastrointestinal disorders. We first performed interviews in 3 countries among IBS and GP. This resulted in a 43-item pilot questionnaire (17 symptom items with 24h recall period and 26 impact items with 7-day recall). Psychometric validation is reported.

Methods: 100 subjects (60 IBS, 40 GP) complaining of GRS were included in each of the 3 countries (UK, Spain, France). Among the 100 subjects, 30 were asked to repeat the IGQ after a 7-day interval on paper or electronically. Convergent/divergent (IGQ vs functional Digestive Disorders Quality of Life - FDDQL) and known-group validity (IGQ vs IBS-SSS) and test-retest reliability (intraclass correlation, ICC) were checked.

Results: 305 subjects were included (UK: 105; Spain: 100; France: 100), with 186 IBS (IBS-C: 68; IBS-D: 61; IBS-M: 57), and 119 GP. Mean age was 42±14 yrs, 69% were female. 26 items were deleted (high floor effect, inter-item correlation, cross-loading or no clear loading). Confirmatory FA on the remaining 17 items (7 symptom and 10 impact items) yielded a 6-factor structure (67% of the variance) with respectively bloating (6 items), flatulence (3), belching (2), bad breath (2), stomach rumbling (2) and difficult gas evacuation (2). Total scores (0-100 were worse among IBS (75±19) vs GP (66±22), p< 0.001. IGQ total and bloating scores were correlated with FDDQL global, Discomfort and Diet dimension scores (r between 0.42-0.68). IGQ total score got worse in parallel with IBS-SSS (r=0.24, p=0.0006). The correlation between the completion of IGQ in paper vs electronic among these 67 stable subjects was high (ICC: 0.77 for global score).

Conclusion: IGQ is a robust instrument for capturing and measuring gas related symptoms. The final 17-item questionnaire has good psychometric properties and is available in paper and electronic versions in 3 languages.