Italian validation of the SMA independence scale-upper limb module.

Spinal muscular atrophy (SMA) is a progressive disorder caused by SMN1 mutations. While therapies have changed its course, current motor scales often miss aspects. This study aimed to validate the Italian SMA Independence Scale (SMAIS-ULM) for reliability, applicability, and expansion across diverse SMA phenotypes. Patients with genetically confirmed 5qSMA were recruited from 12 Italian centers. Analyses included Intraclass Correlation Coefficients (ICCs) for test-retest reliability, the Kruskal-Wallis for group comparisons, and the Spearman correlations with functional measures. Ceiling/floor effects were defined as ≥ 85% of a group reaching the maximum or minimum score. The study analyzed 472 completed questionnaires: 263 from caregivers (mean age 26.4 ± 17.6; 29 SMA I, 123 SMA II, 104 SMA III, 7 presymptomatic) and 209 from patients (mean age 33.1 ± 16.4; 3 SMA I, 101 SMA II, 104 SMA III; 1 SMA IV), including 195 matched caregiver-patient pairs. ICC was conducted in 29 caregivers and 31 patients; values ranged from 0.97 to 1.00. SMAIS-ULM scores differed by SMA type, with SMA III/presymptomatic subjects scoring higher than SMA I/II (p < 0.001) and walkers scoring higher than sitters/non-sitters (p < 0.001). Floor effects were found in 18.9% of non-sitters and 50% of walkers, with comparable patterns in patient responses. Strong correlations with functional measures were found, with no significant differences between caregiver and patient reports.

Conclusion

The findings confirm the reliability and validity of the SMAIS-ULM as an effective tool for measuring functional independence in individuals with SMA, both from the caregiver and patient perspectives.