AIM: To evaluate the structural validity, internal reliability, and measurement invariance of the Pediatric Evaluation of Disability Inventory - Patient Reported Outcome (PEDI-PRO), a measure of functional performance of discrete tasks required to participate in everyday life situations important for adulthood. METHOD: This was a cross-sectional study with 306 young people aged 14 to 22 years (mean 18 years 10 months, SD 2 years 5 months) with developmental disabilities (43.1% autism spectrum disorder only, 23.9% intellectual disability, 17.6% other disability, 11.4% both autism spectrum disorder and intellectual disability, 3.9% missing) completed the PEDI-PRO. Following COnsensus-based Standards for selection of health Measurement INstruments (COSMIN) criteria, we conducted a confirmatory factor analysis, applied a Rasch rating-scale model, examined Cronbach's alpha, Rasch person reliability and separation coefficients, and differential item functioning (DIF). RESULTS: Structural validity was good for the daily activities and mobility domains, and acceptable for the social/cognitive domain. The 3-point Likert response scale functioned as intended. All domains demonstrated acceptable internal consistency on all criteria. One or two items in each domain demonstrated DIF, but the impact on all domain scores was less than 1.0 threshold. INTERPRETATION: The cognitively accessible design and innovative conceptual measurement framework probably contributed to these promising findings. The PEDI-PRO addresses a gap in high-quality patient-reported outcome measures that assess priority outcomes for young people with developmental disabilities.
