Key result
Standard functional measures in adult SMA demonstrate excellent short-term test-retest reliability with ICCs >0.95.
Why the study?
Disease-modifying therapies for SMA require standardized follow-up, but short-term changes may reflect measurement variability rather than true clinical change.
Observational (n=44)
No
Effect estimate: ICC >0.95
Commonly used functional measures in adults with SMA show high short-term reliability, establishing that variations up to 10% likely reflect measurement variability rather than true clinical change.
High short-term reliability supports distinguishing error from change in adult SMA; extends validation but leaves open responsiveness assessment.
Background Disease-modifying therapies for spinal muscular atrophy (SMA) require standardized follow-up to interpret treatment response. However, short-term changes may reflect measurement variability rather than true clinical change. We therefore assessed the test-retest reliability and relationships of routinely used outcome measures in adults with SMA using two standardized evaluations performed within a two-week interval. These assessments included motor function, upper-limb strength and dexterity, ambulatory performance, and respiratory function. Results Forty-four adults with SMA type 2 or 3 were included. No significant change was observed between test and retest visits. Most outcomes demonstrated excellent reproducibility, with intraclass correlation coefficients (ICC) >0.95. Measurement errors were low, with relative standard errors of measurement below 10% for most outcomes. Strong correlations were observed among most outcomes ( p < 0.001). Conclusions Commonly used functional measures in adults with SMA show high short-term reliability. Based on reliability, measurement error, and inter-test correlations, grip strength, MFM, RULM, and FVC appear to be among the most reliable measures, although RULM may be limited by known ceiling and floor effects.
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García-Alcántara et al. (2026) conducted an observational in Spinal muscular atrophy (SMA) type 2 or 3 (n=44). Standardized functional assessments vs. Retest assessment was evaluated on Test-retest reliability (Intraclass correlation coefficients) (ICC >0.95). Commonly used functional outcome measures in adults with spinal muscular atrophy, including grip strength, MFM, RULM, and FVC, demonstrated excellent short-term test-retest reliability with intraclass correlation coefficients >0.95.
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