Rasch Analysis of the Motor Function Measure in Patients with Congenital Muscle Dystrophy and Congenital Myopathy

Vuillerot C, Rippert P, Kinet V, Renders A, Jain M, Waite M, Glanzman AM, Girardot F, Hamroun D, Iwaz J, Ecochard R, Quijano-Roy S, Bérard C, Poirot I, Bönnemann CG; CDM MFM study group.
Arch Phys Med Rehabil. 2014. 57(9-10):587-99.
The main goal of the study is to provide a valid outcome measure in order to monitor treatment effects in patients with congenital disorders of muscle.
289 patients, aged 5 to 77 years old, were enrolled and the three domains of the MFM were examined using a Rasch analysis.
The original 32-item MFM did not fit the Rasch model expectations enough in neither of its domains. Switching from a four- (0,1,2,3) to a three-category response scale (0,1,2) restored response order in 16 items. Various additional checks suggested the removal of seven items. The resulting 25-item MFM demonstrated a good fit to the Rasch model. Domain 1 was well targeted to the whole severity spectrum whereas Domains 2 and 3 were better targeted to severe cases. The reliability coefficients of the Rasch MFM-25 suggested sufficient ability for each summed score to distinguish between patient groups.

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Keywords: Rasch analysis, congenital muscular dystrophy, congenital myopathy, motor function assessment, outcome measure