Aim: This study examined the reliability, validity and factor structure of the Swedish version of the IMPACT-III questionnaire for assessing health-related quality of life in children with inflammatory bowel disease.

Methods: We recruited 202 participants aged eight to 18years, who were enrolled from 16 of the 23 paediatric gastroenterology clinics across Sweden during 2010-2013. This cross-sectional study compared two versions of the IMPACT-III questionnaire - one with six factors and 35 items and one with four factors and 19 items - plus the Paediatric Quality of Life Inventory 4.0 Generic Core Scale. Disease activity was assessed and defined as active or inactive.

Results: The mean total score for the six-factor IMPACT-III scale was 143.7/175, with a standard deviation (SD) of 17.9. There was a significant difference in mean total scores between the 133 children with inactive disease (147.8, SD: 14.9) and the 52 with active disease (133.0, SD: 20.3). Confirmatory factor analysis showed that the four-factor scale was more robust than the original six-factor scale. Concurrent validity and discriminant validity were high for both versions.

Conclusion: The Swedish version of the IMPACT-III questionnaire was valid and reliable, but the shorter, four-factor version is quicker and may be more convenient in clinical settings.