Development and validation of a modified performance-oriented mobility assessment tool for assessing mobility in children with hypophosphatasia

PURPOSE: To modify the Performance-Oriented Mobility Assessment-Gait (POMA-G) subtest and validate this modified POMA-G (mPOMA-G) in children with hypophosphatasia (HPP), a rare metabolic disorder that can manifest with musculoskeletal symptoms that impair mobility and ambulation. METHODS: Based on feedback from an expert panel, the POMA-G was modified by removing gait initiation/path assessments and expanding the rating scale for step length/continuity to capture aspects of observational gait analysis relevant to children with HPP. Three trained physical therapists used the mPOMA-G for video-based assessments of gait in 14 children with childhood HPP who participated in a clinical study of asfotase alfa or in a natural history study. Intraclass correlation coefficients (ICCs) were calculated to determine interrater and intrarater agreement. Concurrent validity was evaluated by correlations with other validated assessment tools. RESULTS: Across 192 observations from available videos, interrater and intrarater agreement of mPOMA-G scores was significant (ICCs: 0.76 for both; [Formula: see text] 0.001). mPOMA-G scores had strong concurrent validity with the Childhood Health Assessment Questionnaire, Pediatric Outcomes Data Collection Instrument Transfer and Mobility Scale, Sports and Physical Function subscale, and 6-Minute Walk Test (all [Formula: see text] 0.0002). CONCLUSION: The mPOMA-G is a reliable and valid measure for detecting clinically significant impairments in children with HPP.