Quality of life in patients with inflammatory bowel disease: Translation, data quality, scaling assumptions, validity, reliability and sensitivity to change of the Norwegian version of IBDQ

Background: The use of quality of life (QoL) questionnaires in clinical medicine must be based on instruments that are reliable and valid. The aim of this study was to describe the translation of the Inflammatory Bowel Disease Questionnaire (IBDQ) into Norwegian, its scaling assumptions and the psychometric properties of the translated questionnaire. Method: All patients included were recruited from an ongoing epidemiological study started in 1990 (the IBSEN trial), based on the registration of undiagnosed cases of Crohn disease (CD) or ulcerative colitis (UC) in subjects permanently residing in the study area the year before registration. At the 5-year follow-up visit in the hospital, all patients between 18 and 75 years of age were invited to participate in this QoL study, and those willing were interviewed and asked to complete the two QoL questionnaires, IBDQ and SF-36, on two different occasions separated by 6 months. The IBDQ was tested for validity, reliability and responsiveness. Results: In total, 497 patients (93%) completed the IBDQ questionnaire at visit 1, and 493 (92%) completed SF-36. The mean age was 43.3 years, 48% were female. We found that the Norwegian version of the IBDQ (N-IBDQ) consists of five underlying dimensions in contrast to the four dimensions previously reported. Psychometric testing of the N-IBDQ indicates that the questionnaire is valid, reliable, has a high degree of responsiveness and that the results are comparable to those reported from other groups, even though our findings are based on a different factorial structure than the original McMaster version. Conclusion: The N-IBDQ consists of five different dimensions in contrast to the four dimensions previously reported. Good item internal consistency, validity, reliability and responsiveness were demonstrated.