The Motor Function Measure domain D1 can reliably measure motor function in ambulant patients with Duchenne muscular dystrophy (DMD), according to a recently published study in Clinical Rehabilitation.

Although there is currently no cure for DMD, great advances have been made to improve quality of life and survival as well as decrease disease progression. Therefore, there is an increasing need for tools that can accurately measure physical function in these patients. 

The 32-item Motor Function Measure (MFM) is one of the most widely used scales to measure motor function in patients with DMD; evidence shows that the scale is valid, reliable, and produces reproducible results. However, it was yet to be validated by a modern psychometric method, such as Rasch analysis. Hence, the authors aimed to analyze the scale using Rasch analysis in a cohort of over 170 patients with DMD.


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The MFM assesses 3 functional domains, standing position and transfers (D1), axial and proximal motor function (D2), and distal motor function (D3). Response scores range from 0 to 3, with 0 representing the inability to complete the task and 3 indicating the ability to complete the task normally.

All patients included in the study had been genetically diagnosed with DMD, were over 24 months of age, and could walk at least 10 meters with or without technical assistance. None of the included patients had any cognitive impairment. Patients with severe pain that could affect motor function were excluded from the study.

“The following psychometric properties were tested: item-person targeting, reliability and separation, item fit, category functioning, dimensionality, and local dependency,” the authors wrote.

Item targeting of the D1 domain was acceptable, which means there was a match between the range of motion measured by the MFM and the range of motion measured in the patient sample; however, domains D2 and D3 fell below the expectations of the Rasch model. 

The authors recommend that D2 and D3 domains are not optimal for this group of patients and should be used with caution.

“The preliminary findings supported that the Motor Function Measure domain D1 was a reliable and valid measure in our sample,” the authors concluded.

Reference

Huang M, Chen T, Zhou C, et al. Rasch analysis of the 32-item motor function measure in ambulant patients with Duchenne muscular dystrophy. Clin Rehabil. Published online October 26, 2022. doi:10.1177/02692155221135843