RASCH ANALYSIS OF THE PEDIATRIC EVALUATION OF DISABILITY INVENTORY-COMPUTER ADAPTIVE TEST (PEDI-CAT) ITEM BANK FOR CHILDREN AND YOUNG ADULTS WITH SPINAL MUSCULAR ATROPHY

Introduction: In this study we evaluated the suitability of a caregiver-reported functional measure, the Pediatric Evaluation of Disability Inventory-Computer Adaptive Test (PEDI-CAT), for children and young adults with spinal muscular atrophy (SMA). Methods: PEDI-CAT Mobility and Daily Activities domain item banks were administered to 58 caregivers of children and young adults with SMA. Rasch analysis was used to evaluate test properties across SMA types. Results: Unidimensional content for each domain was confirmed. The PEDI-CAT was most informative for type III SMA, with ability levels distributed close to 0.0 logits in both domains. It was less informative for types I and II SMA, especially for mobility skills. Item and person abilities were not distributed evenly across all types. Conclusions: The PEDI-CAT may be used to measure functional performance in SMA, but additional items are needed to identify small changes in function and best represent the abilities of all types of SMA.