New SMA era: A broad-range tiered assessment of function for the evolving SMA phenotype (EVOLVE-SMA)

The clinical course of Spinal Muscular Atrophy (SMA) has been transformed by new disease-modifying therapies (DMT). Before DMT, the clinical course of SMA was marked by an inflection point between developmental improvement and degenerative functional losses. The well-established SMA classification by "type" was based upon the age and functional level at which this inflection point manifested. Following DMT, the natural history of SMA has evolved. The evolution of the SMA clinical course following DMT thus necessitates an updated means to characterize individuals with SMA.

To address both clinical and research needs, an updated assessment should target meaningful function; apply broadly across the range of SMA; maximize the granularity of functional tiers with minimal compromise of reliability; require minimal or no specific training; and be validated with measurable consistency between both naïve and experienced clinicians, and between these clinicians and members of the SMA community.

Development of the Functional Ability Scale for Evolving SMA (EVOLVE-SMA) proceeded as an iterative scale creation and refinement process using retrospective cohorts (for design, reliability, and validity) followed by prospective assessments of real-world feasibility and reliability.

Excellent interrater reliability (ICC >0.9, p < 0.001) was established between expert and novice clinicians (physician and physical therapist) and clinicians versus SMA community members.

EVOLVE-SMA is a tiered evaluation of function applicable to the new DMT-treated era of SMA. It is a simple, granular, and reliable means to assess meaningful functions that will have value to research, resource allocation, and individual clinical care.