The IMPACT-III (HR) questionnaire: a valid measure of health-related quality of life in Croatian children with inflammatory bowel disease.

BACKGROUND AND AIMS To assess the reliability and validity of IMPACT-III (HR), a disease-specific, health-related quality of life instrument in Croatian children with inflammatory bowel disease. METHODS In a multicenter study, 104 children participated in a validation study of IMPACT-III (HR) cross-culturally adapted for Croatia. Factor analysis was used to determine optimal domain structure for this cohort, analysis of Cronbach's alpha coefficients to test internal reliability, ANOVA to assess discriminant validity, and correlation with Pediatric Quality of Life Inventory, Version 4.0 (PedsQL) using Pearson correlation coefficients to assess concurrent validity. RESULTS Cronbach's alpha for the IMPACT-III (HR) total score was 0.92. The most robust factor solution was a 5-domain structure: Symptoms, Concerns, Socializing, Body Image, and Worry about Stool, all of which demonstrated good internal reliability (α=0.60-0.89), but two items were dropped to achieve this. Discriminant validity was demonstrated by significant differences (P<0.001) in mean IMPACT-III (HR) scores between quiescent and mild or moderate-severe disease activity groups for total (148 vs. 139 or 125) and following factor scores: Symptoms (84 vs. 71 or 61), Socializing (91 vs. 83 or 76), and Worry about Stool (significant only between quiescent and moderate-severe groups, 90 vs. 62, respectively). Concurrent validity of IMPACT-III (HR) with PedsQL showed significant correlation, which was strongest when similar domains were compared. CONCLUSION IMPACT-III (HR) appears to be useful tool to measure health-related quality of life in Croatian children with Crohn's disease and ulcerative colitis.