Supplementary Material for: Validation of the Portuguese version of IBD-Control questionnaire and comparison with IBD-Disk

Introduction: The IBD-Control questionnaire and IBD-Disk are two patient-reported outcome measures designed to evaluate the impact of Inflammatory Bowel Disease (IBD) on different health domains. Unlike IBD-Disk, there is no fully published validated Portuguese version of IBD-Control. Furthermore, the two instruments have not yet been compared. We aimed to translate and validate IBD-Control in Portugal and compare it with IBD-Disk.
Methods: After translation into Portuguese, the IBD-Control was administered to IBD patients, at baseline (T0), after 1-4 weeks (T1) and 3 months (T2). Patients also completed the Portuguese versions of the PRO2, EQ-5D, short-IBDQ and IBD-Disk. We assessed reliability, validity, responsiveness and interpretability of IBD-Control. We compared the usability (3 questions) and the ability to identify good disease control (AUC) of IBD-Control and IBD-Disk.
Results: At T0, the IBD-Control was completed by 142 patients (108 Crohn's disease, 34 ulcerative colitis). At T1 and T2, 68 and 101 patients completed the questionnaire, respectively. Factor analysis confirmed the one-dimensionality of the scale with 8 items (IBD-Control-8). Internal consistency (Cronbach's alpha) was 0.80. Test-retest reproducibility for stable patients (n=54) was high (intraclass correlation coefficient-0.86). IBD-Control-8 significantly correlated (r between 0.55 and 0.82; p≤0.001) with PRO2, EQ-5D, short-IBDQ and IBD-Disk. The variation in IBD-Control-8 between T0 and T2 correlated significantly (r between 0.48 and 0.53; p≤0.01) with the variation in PRO2 (only for Crohn's disease), short-IBDQ and IBD-Disk. The IBD-Control-8 significantly discriminated between well and poorly controlled disease (15±2 vs 11±4; p<0.001). No significant differences were observed between IBD-Control-8 and IBD-Disk regarding usability and the ability to identify good disease control (AUC-0.79 vs 0.76, respectively).
Conclusions: The IBD-Control is reliable and valid for measuring disease control from the perspective of patients with IBD in Portugal, presenting no significant differences regarding usability and assessment of disease control when compared to IBD-Disk.