Purpose: The KIDSCREEN questionnaire for health-related quality of life (HRQOL) assessments in children and adolescents was simultaneously developed across 13 European countries, and it was subsequently translated and culturally adapted to over 30 different languages across the world. The aim of this study was to evaluate the measurement equivalence of the KIDSCREEN-27 across Serbian and Iranian children and adolescents.
Methods: The items in the KIDSCREEN-27 were analyzed for differential item functioning (DIF) across Iranian and Serbian populations using ordinal logistic regression with three different criteria. The sample included 330 Iranian and 329 Serbian children and adolescents and 330 and 314 of their parents, respectively.
Results: Across the two samples, DIF was detected in 16 (59 %) of 27 items in the child self-reports and in 20 (74 %) of 27 items in the parent/proxy report. However, using alternative criteria based on magnitude detected for DIF, only three items in the parent/proxy report showed significant DIF.
Conclusion: Our study provided more evidence that the KIDSCREEN-27 possesses DIF items across different cultures, but their impact is probably small, and the questionnaire could be used for cross-cultural HRQOL comparisons.