Validation of the inflammatory bowel disease questionnaire in Swedish patients with ulcerative colitis

Background: The Inflammatory Bowel Disease Questionnaire (IBDQ) is a diseas e-specific health-related quality of Life (HRQOL) questionnaire including f our dimensions and a sum score. The aim of this study was to assess the int ernal and external validity, reliability, and sensitivity of a Swedish vers ion of the IBDQ. Methods: Three hundred consecutive patients with ulcerativ e colitis completed the IBDQ and three other health-related quality of life questionnaires (the Rating Form of IBD Patient Concerns (RFIPC), the Shea Form-36 (SF-36) and the Psychological General Well-Being (PGWB) index). Dis ease activity was evaluated using a 1-week symptom diary, blood tests and r igid sigmoidoscopy. One hundred and fourteen patients filled in the questio nnaire a second time, of whom 75 had been in stable remission for over 6 mo nths and 39 had a significant clinical change in disease activity. Results: Factor analysis of the 32 IBDQ items did not support the four dimensional scores. The dimensional scores had sufficient convergent validity, but low discriminative validity and homogeneity. The homogeneity was also low for t he sum score. The inter-dimensional correlations were high. The concurrent validity was supported by correlations between the dimensional scores and o ther measures of disease activity and HRQOL. Patients in relapse scored sig nificantly less on the sum score and the four dimensions compared to patien ts in remission. The test-retest correlations for the dimensional scores we re 0.40-0.76. Patients with a change in disease activity during the 6-month follow-up period had a significant change in IBDQ scores not found in thos e who remained in remission. Conclusions: The Swedish version of the IBDQ h ad external validity and was shown to be a reliable and sensitive measure o f HRQOL in ulcerative colitis, though there are some concerns regarding the internal validity. The use of a sum score was not supported and the questi onnaire may benefit from a redivision of items into dimensions with better homogeneity and discriminative validity.