Outcome measures in a cohort of ambulatory adults with spinal muscular atrophy. Issue 2 (11th December 2019) - Elsheikh, Bakri
Abstract: Introduction: With the advent of disease‐altering therapies for spinal muscular atrophy (SMA), there is a requirement to better characterize outcome measures, particularly in milder forms of disease. Methods: Maximal voluntary isometric contraction testing and 6‐minute walk test (6MWT) performed in ambulatory SMA adults as part of the SMA‐VALIANT trial were analyzed. Test–retest reliability and correlation with other candidate biomarkers and outcomes were investigated. Results: Maximal voluntary isometric contraction testing and 6MWT showed good test–retest reliability (intraclass correlation coefficient = 0.98 and 0.85, respectively). Maximal voluntary isometric contraction testing and 6MWT demonstrated very strong correlation ( r = 0.83, P <. 0001), and each correlated with the SMA Functional Rating Scale ( r = 0.7, P < .0001 and r = 0.65, P = .0001, respectively), lean muscle mass ( r = 0.68, P < .0001 and r = 0.56, P = .001, respectively), and ulnar compound muscle action potential ( r = 0.57, P = .0008 and r = 0.47, P = .008, respectively). Discussion: Maximal voluntary isometric contraction testing and 6MWT are suitable outcomes for use in ambulatory adults with SMA. Maximal voluntary isometric contraction testing may be preferable because of superior test–retest reliability and closer associations with other outcomes and biomarkers of neuromuscular function.