Rasch analysis of the self-reported PedsQL™ 4.0 Generic Core Scales by Australian children

Purpose: The Pediatric Quality of Life Inventory™ Version 4.0 Generic Core Scales (PedsQL GCS), comprising 23 items covering four subscales (physical, emotional, social, and school functioning), is a widely applied generic measure of childhood health-related quality of life (HRQoL). This study aimed to assess the psychometric performance of the self-reported Child version in an Australian general population of children using psychometric criteria based on Rasch measurement theory. Methods: To minimise type I error, a random sample of n = 500 was drawn from 1,874 Australian children aged 11–12 years who participated in the Longitudinal Study of Australian Children and completed the PedsQL GCS Child self-report measure. The partial credit model was applied. The following properties were assessed: unidimensionality, model goodness of fit, model reliability, targeting, item fit, threshold ordering, differential item functioning (DIF), and local dependency. Results: Areas of poor performance included: weak support for unidimensionality of school functioning subscale; only emotional functioning subscale showing sufficient model goodness of fit; poor targeting, suggesting that item thresholds are limited in discriminating HRQoL differences in this cohort; seven items showing disordered thresholds; and five pairs of items being locally dependent. Only two items showed poor fit, and there was no evidence of non-uniform DIF regarding sex and age. Conclusion: Not all Rasch measurement criteria were satisfied by the PedsQL GCS Child self-report measure applied in Australian children. This Rasch-based psychometric evaluation identified potential areas of improvement that can complement the known conceptual, practical, and classical psychometric strengths of the PedsQL GCS.