Reliability of Spinal Muscular Atrophy Functional Rating Scale (SMAFRS) in Ambulatory Adults with Spinal Muscular Atrophy. (P4.452)

Objective: To investigate the reliability of SMAFRS in ambulatory adults with spinal muscular atrophy (SMA). Background: SMA is a motor neuron disorder resulting from reduced survival motor neuron (SMN) protein levels. While nusinersen, an antisense oligonucleotide therapy to increase SMN, was approved for all types of SMA, there is minimal data on adults with SMA. Therefore, identifying outcome measures to track and quantify treatment response has become increasingly important. SMAFRS has shown to better discriminate between adults with SMA having 3 versus 4 SMN2 copies as compared to quantifying muscle strength. Similarly, we have previously showed significant modified SMAFRS score differences between adults with SMAtype 2 versus type 3 patients. In this study, we investigated SMAFRS in ambulatory adults with SMA (AA-SMA). Design/Methods: We analyzed data obtained during two screening visits performed 4 weeks apart in 32 participants (19 M;13F) ages (17–55; 36.2±9.2/mean± SD) enrolled in the VALIANT trial. Results of the SMAFRS, maximum voluntary isometric contraction testing (MVICT) of elbow and knee flexion and extension and hand grip, 6-minute walk test (6MWT) and ulnar compound muscle action potential amplitude (CMAP) was analyzed. Spearman’s correlation coefficients were calculated to determine the association between the measures, and p values less than 0.05 were considered significant. Results: All participants completed the SMAFRS, and the mean SMAFRS was 32.6 ±4.0 for the first visit and 33.1±4.2 for the follow up visit. Test-retest reliability was good with a correlation coefficient of 0.86. SMAFRS showed a positive correlation with MVICT average sum score (r= 0.67, p Conclusions: SMAFRS testing in AA-SMA is feasible, has good test-retest reliability, and shows good correlation with muscle strength and 6MWT. SMAFRS should be assessed as a candidate outcome measure tool to monitor nusinersen treatment. Study Supported by: This project was funded by Cure SMA Disclosure: Dr. Elsheikh has nothing to disclose. Dr. King has nothing to disclose. Dr. Arnold has nothing to disclose. Dr. Kissel has received research support from Novartis, Biomarin, Cytokinetics, CSL Behring, Avexis, Ionis Pharmaceuticals, Quintiles, Axelacare.