Objective: The EuroQol EQ-5D is a generic questionnaire for describing and valuing patients' health-related quality of life. The purpose of the study was to analyse the construct validity, criterion validity, test-retest reliability and responsiveness of the EQ-5D in patients with inflammatory bowel disease.
Methods: 152 consecutive patients with inflammatory bowel disease (123 with Crohn's disease and 29 with ulcerative colitis) completed the EQ-5D, the SF-36 and the Inflammatory Bowel Disease Questionnaire (IBDQ). Of the study group, 66 patients filled in the EQ-5D a second time after a 2-week gap, including a transition question. Disease activity was measured by the Crohn's Disease Activity Index (CDAI) and by Rachmilewitz's Clinical Activity Index (CAI).
Results: The EQ-5D showed a moderate ceiling effect. Correlation between the EQ-5D visual analogue scale (EQ VAS) score and CDAI/CAI was r = -0.65/r = -0.71 (both P < 0.001). Levels of responses to EQ-5D items and the EQ VAS score were significantly better for patients in remission than for patients with active disease (all P < 0.01). For the total sample, coefficients of correlation between the EQ VAS score and SF-36 and IBDQ scores ranged between 0.37 and 0.73 (all P < 0.0001). When repeated, the EQ-5D was reliable in stable patients (intraclass correlation coefficient for EQ VAS = 0.77, kappa statistic for items 0.39 to 1.00); the EQ VAS was responsive in patients who, in the transition question, indicated an improvement in health state (effect size 0.79).
Conclusions: The EQ-5D is reasonably valid, reliable and responsive in patients with inflammatory bowel disease. It can be used to generate preference-based valuations of health-related quality of life in inflammatory bowel disease.