BACKGROUND: No validated instruments have been developed to measure work disability in Crohn's disease (CD). The aim of our study was to develop and validate a CD perceived work disability questionnaire (CPWDQ). METHODS: Development phase: an initial questionnaire containing 52 items was obtained from patients' interviews plus additional sources; it was completed by 106 patients and the 16 most significant items were selected using a psychometric method in order to create the CPWDQ. Validation phase: The validation assessed the questionnaire's convergent validity, discriminant validity, test-retest reproducibility, and internal consistency in 108 patients. Spearman rank correlation, t-test, intraclass correlation, and Cronbach's alpha were used for the analysis. RESULTS: Convergent validity was confirmed by good correlations between the CPWDQ and: clinical activity (r = 0.59, P < 0.01), the Short Inflammatory Bowel Disease Questionnaire, IBDQ-9, (r = 0.76, P < 0.001), Euroqol-5D (r = 0.53, P < 0.01), and overall work impairment (WPAI_CD) r = 0.66 (P < 0.01). Discriminant validity: CPWQ scores were higher in patients expected to have more severe disability, that is, in patients with active disease (n = 38) 32.3 +/- 7.3 versus inactive (n = 70) 22.6 +/- 5.9 (P < 0.001), in those requiring previous sick leave 30.7 +/- 7.5 (n = 45) versus no sick leave 22.6 +/- 6.6 (n = 63) (P < 0.01), and in those requiring hospitalization 32.2 +/- 8.6 (n = 18) versus no hospitalization 24.7 +/- 7.1 (n = 90) (P < 0.01). Internal consistency was also good (Cronbach's alpha = 0.89). Reproducibility: CPWDQ measures obtained 2 weeks apart showed an excellent intraclass correlation coefficient: 0.89 (95% CI: 0.83-0.93). CONCLUSIONS: The CPWDQ seems to be a valid, reliable tool for measuring subjective work disability in CD.
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