Validation of the IBD-Disk in a Portuguese cohort.

Objective: The aim of this study was to validate the IBD-Disk in a Portuguese cohort according to the COnsensus-based Standards for the selection of the health Measurement INstruments (COSMIN) recommendations.

Methods: After translation of the original IBD-Disk to Portuguese, a group of IBD patients was invited to complete the IBD-Disk at baseline (T0), after 1-4 weeks (T1) and after more than 3 months (T2), from July 2020 to February 2021. At T0 and T2, the patients also completed the IBD Disability Index. We evaluated reliability (internal consistency, test-retest, interrater reliability and measurement error), construct validity, responsiveness, interpretability of IBD-Disk, sociodemographic and clinical factors associated with IBD-Disk.

Results: At T0, 154 patients (107 - Crohn's disease; 46 - ulcerative colitis) completed the IBD-Disk; 1 - IBD-unclassified). At T1 and T2, 64 and 114 patients repeated the questionnaire, respectively. Factor analysis confirmed the unidimensionality of the scale and reduced the final version to 10 items. Internal consistency was excellent with a Cronbach's α of 0.916. The intraclass correlation coefficient was 0.95 for test-retest (T0 and T1). To evaluate construct validity, the IBD-Disk was compared with the IBD Disability Index and Manitoba IBD Index with a significative positive correlation (r = 0.850 and r = 0.459, respectively; P < 0.001 for both). IBD-Disk scores ranged from 0 to 93 with a mean of 38.18 ± 25.39. Female sex, professional inactivity, longer IBD duration and clinical activity were associated with significantly higher IBD-Disk scores.

Conclusion: The Portuguese version of IBD-Disk is a reliable and valid tool to assess disability in Portuguese IBD patients.