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; P< 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 P⩽ 0.0002).

CONCLUSION

The mPOMA-G is a reliable and valid measure for detecting clinically significant impairments in children with HPP.