Abstract
Introduction: The 8-item Inflammatory Bowel Disease control Questionnaire-8 (IBDcQ-8) is a patient-reported measure designed to capture the core domains of disease control and quality of life. The aim of this study was to evaluate the validity and reliability of the Persian version of the IBDcQ-8 in the Iranian IBD population.
Methods: A standardized forward–backward translation procedure was employed to adapt the questionnaire into Persian. Content validity was evaluated through structured interviews with a panel of 10 evaluators. Construct validity was examined by structured interview and clinical visits of 101 patients. Harvey Bradshaw Index (HBI), partial Mayo score, and IBD Questionnaire (IBDQ) were used as comparator instruments. Patients’ responses were compared with clinical global assessment, Harvey Bradshaw Index (HBI), partial Mayo score, IBDQ score , and laboratory markers using Spearman’s rank correlation. Test–retest reliability was evaluated by calculating the intraclass correlation coefficient (ICC) between the two subsequent interviews. A P-value<0.05 was considered statistically significant.
Results: Half of the subjects (n=51 (50.5%)) were female. The mean age was 38 years (SD=14). Sixty-seven patients (66%) had UC. IBDcQ-8 scores showed strong correlations with HBI and IBDQ, and moderate correlations with the partial Mayo score, CRP, and clinical evaluation at the first visit (P-value<0.05). Agreement was excellent for one-day follow-up (ICC=0.82, 95% CI: 0.71–0.89, P<0.001), and moderate for two-week follow-up (ICC=0.61, 95% CI: 0.44–0.73, P<0.001).
Conclusion: The Persian version of the IBDcQ-8 questionnaire demonstrated robust validity and acceptable reliability even when administered by telephone interview, supporting its usefulness for evaluating disease-specific quality of life in patients with IBD and its applicability in future studies.