T.P.42: Comparison of three scales of motor function in two subtypes of patients with congenital muscular dystrophy

Abstract

Comparisons of clinical outcome measures of motor performance to be used in clinical trials in Congenital Muscular Dystrophy subtypes are limited. However, redundancy, discriminant validity, and ceiling and floor effects of motor function measures are an important consideration in optimizing the use of outcome measures clinical trials. Methods: We conducted a study to compare the Motor Function Measure 32 (MFM32), the Hammersmith Functional Motor Scale (HFMS), and the North Star Ambulatory Assessment (NSAA) in 29 subjects with COL6-RM and LAMA2-RD. We analyzed concurrent validity using Spearman rank order correlation, discriminant analysis using Wilcoxon Mann Whitney test, and floor and ceiling effects using a cut off of 20% for each item. We hypothesized that the HFMS and NSAA would expand the motor function assessment of the MFM32 in both extremes of functional limitations and disease severity (NSAA for higher functioning/less severe and HFMS for lower functioning/more severe). Concurrent validity for the MFM32, HFMS, and NSAA was strong as evidenced by large correlations (ranging 0.76–0.93, <i>p</i><0.0001) between the three measures. The MFM32 and HFMS scores were able to discriminate individuals by ambulatory status (<i>p</i><0.001). The HFMS, NSAA, and MFM32 had a floor effect, but the MFM32 floor effect was limited to Domain 1 (standing and transfers). The MFM32 also had a ceiling effect distributed across all 3 domains. All three measures correlated highly, but the HFMS and MFM32 may be redundant for use in the same study. The NSAA is useful as a complementary outcome measure in ambulatory individuals.