Development and validation of the Crohn's disease perceived work disability questionnaire

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).

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.

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).

The CPWDQ seems to be a valid, reliable tool for measuring subjective work disability in CD.