Validity and Reliability of the 32-Item Motor Function Measure in 2- to 5-Year-Olds with Neuromuscular Disorders and 2- to 25-Year-Olds with Spinal Muscular Atrophy
Dylan Trundell, Stephanie Le Scouiller, Ksenija Gorni, Timothy J. Seabrook, Carole Vuillerot, the SMA MFM Study Group
Abstract
INTRODUCTION: To investigate the validity and reliability of the 32-item Motor Function Measure (MFM32) in individuals with neuromuscular disorders (NMD), including spinal muscular atrophy (SMA), aged 2-5 years, and in non-ambulant individuals with Types 2 or 3 SMA, aged 2-25 years. METHODS: Test-retest reliability (intraclass correlation coefficient [ICC]), internal consistency (Cronbach's alpha [α]), convergent validity (Spearman rank-order correlations), and known-groups validity (analysis of covariance comparing groups defined by the Clinical Global Impression of Severity [CGI-S] scale and Vignos grade) were calculated. The analysis was performed on a dataset provided by Hospices Civils De Lyon, extracted from the multinational MFM32 database. A total of 165 individuals were included in the analyses, of whom 84 were in the NMD group (aged 2-5 years) and 81 were in the SMA group (aged 2-25 years). RESULTS: Strong evidence of test-retest reliability (ICC: 2- to 5-years' population = 0.94-0.95; 2- to 25-years' population = 0.97), internal consistency (Cronbach's α: 2- to 5-years' population = 0.96; 2- to 25-years' population = 0.95), convergent validity (2- to 5-years' population: CGI-S rho = - 0.84, Vignos grade rho = - 0.79; 2- to 25-years' population: CGI-S rho = - 0.49), and known-groups validity (all P < 0.001) were demonstrated. CONCLUSIONS: These analyses provide supportive evidence of the validity and reliability of the MFM32 in younger individuals with NMDs, aged 2-5 years, and in non-ambulant individuals with Types 2 or 3 SMA, aged 2-25 years, supporting the use of the MFM32 across a wide age range.