Design and validation of a German version of the GSRS-IBS - an analysis of its psychometric quality and factorial structure

BACKGROUND Currently, a suitable questionnaire in German language is not available to monitor the progression and evaluate the severity of irritable bowel syndrome (IBS). Therefore, this study aimed to translate the Gastrointestinal Symptom Rating Scale for Irritable Bowel Syndrome (GSRS-IBS) into German and to evaluate its psychometric qualities and factorial structure. METHODS This study is based on a total sample of 372 participants [62.6% female, mean age = 41 years (SD = 17 years)]. 17.5% of the participants had a diagnosis of IBS, 19.9% were receiving treatment for chronic inflammatory bowel disease, 12.1% of the participants were recruited from a psychosomatic clinic, and 50.5% belonged to a control group. All participants completed the German version of GSRS-IBS (called Reizdarm-Fragebogen, RDF), as well as the Gießen Subjective Complaints List (GBB-24) and the Hospital Anxiety and Depression Scale - German version (HADS-D). RESULTS The internal consistency of the RDF total scale was at least satisfactory in all subsamples (Cronbach's Alpha between .77 and .92), and for all subscales (Cronbach's Alpha between .79 and .91). The item difficulties (between .25 and .73) and the item-total correlations (between .48 and .83) were equally satisfactory. Principal axis analysis revealed a four-factorial structure of the RDF items, which mainly resembled the structure of the English original. Convergent validity was established based on substantial and significant correlations with the stomach-complaint scale of the GBB-24 (r = .71; p < .01) and the anxiety (r = .42; p < .01) and depression scales (r = .43; p < .01) of the HADS-D. CONCLUSION The German version of the GSRS-IBS RDF proves to be an effective, reliable, and valid questionnaire for the assessment of symptom severity in IBS, which can be used in clinical practice as well as in clinical studies.