Understanding North Star Ambulatory Assessment total scores and their implications for standards of care using observational data

Abstract

NorthStar Ambulatory Assessment (NSAA) total score (TS) is an ordinal scale to evaluate disease progression and treatment response in ambulatory Duchenne Muscular Dystrophy individuals. Clinical management according to standard of care could be enhanced by understanding how changes in the TS could inform standards of care. Here we describe the associated item performance patterns in the NorthStar Database for ranges of NSAA TS and its timed tests (10 m walk/run and rise from floor). We then compare these patterns depending on whether a participant is on an improving/stable (≤2-point loss in the prior year) or declining (>2-point loss in the prior year) trend. These TS and trends are subsequently linked and referenced to therapy standards of care. We included 761 participants from the UK NorthStar observational clinical database between 5 and 16 years, who were on steroids. Differences and trends in item ability, compensations, and times can suggest specific disease complications and lead towards anticipatory therapy recommendations. Families and therapists can benefit from using the TS and trend to guide therapy management.