Test-retest measurement properties of the MScanFit method for motor unit number estimation in individuals with...

MScanFit is one of the Motor Unit Number Estimation (MUNE) methods considered as a potential biomarker for Amyotrophic Lateral Sclerosis (ALS) diagnosis and clinical trials. We investigated the test-retest measurement properties of MScanFit across multiple muscles in individuals with ALS.

We recorded MUNE from Abductor Pollicis Brevis (APB), Abductor Digiti Minimi (ADM), and Tibialis Anterior (TA) muscles in seventeen adults with ALS separated by 1-2 weeks. Intraclass correlation and concordance correlation coefficients provided reliability estimates. Overall agreement was evaluated using pairedt-tests or the Wilcoxon signed-rank test and an estimation statistical approach. The standard error of measurement and the smallest detectable change provided the extent of agreement.

The reliability coefficients ranged from 0.66 to 0.91. The measurement error was high (standard error of measurement > 10 %). The smallest detectable change was high (24-61 units) at an individual level, although smaller (∼10 units) at a group level (N = 10-30) CONCLUSION: MScanFit has moderate-to-excellent reliability and can reliably detect smaller changes at a group level, but is limited in reliably detecting smaller changes at an individual level.

The MScanFit MUNE can potentially serve as a group-level biomarker in ALS clinical trials.