Background: The Inflammatory Bowel Disease Questionnaire (IBDQ) is a disease-specific health-related quality of life (HRQOL) questionnaire including four dimensions and a sum score. The aim of this study was to assess the internal and external validity, reliability, and sensitivity of a Swedish version of the IBDQ.
Methods: Three hundred consecutive patients with ulcerative colitis completed the IBDQ and three other health-related quality of life questionnaires (the Rating Form of IBD Patient Concerns (RFIPC), the Short Form-36 (SF-36) and the Psychological General Well-Being (PGWB) index). Disease activity was evaluated using a 1-week symptom diary, blood tests and rigid sigmoidoscopy. One hundred and fourteen patients filled in the questionnaire a second time, of whom 75 had been in stable remission for over 6 months 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 the sum score. The inter-dimensional correlations were high. The concurrent validity was supported by correlations between the dimensional scores and other measures of disease activity and HRQOL. Patients in relapse scored significantly less on the sum score and the four dimensions compared to patients in remission. The test-retest correlations for the dimensional scores were 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 those who remained in remission.
Conclusions: The Swedish version of the IBDQ had external validity and was shown to be a reliable and sensitive measure of HRQOL in ulcerative colitis, though there are some concerns regarding the internal validity. The use of a sum score was not supported and the questionnaire may benefit from a redivision of items into dimensions with better homogeneity and discriminative validity.