Abstract
Objectives
To monitor treatment effects in patients with congenital myopathies and congenital
muscular dystrophies, valid outcome measures are necessary. The Motor Function Measure
(MFM) was examined for robustness, and changes are proposed for better adequacy.
Design
Observational study based on data previously collected from several cohorts.
Setting
Nineteen departments of physical medicine or neuromuscular consultation in France,
Belgium, and the United States.
Participants
Patients (N=289) aged 5 to 77 years.
Interventions
None.
Main Outcome Measures
A Rasch analysis examined the robustness of the MFM across the disease spectrum. The
3 domains of the scale (standing position and transfers, axial and proximal motor
function, and distal motor function) were independently examined with a partial credit
model.
Results
The original 32-item MFM did not sufficiently fit the Rasch model expectations in
either of its domains. Switching from a 4- to a 3-category response scale in 18 items
restored response order in 16. Various additional checks suggested the removal of
7 items. The resulting Rasch-scaled Motor Function Measure with 25 items for congenital
disorders of the muscle (Rs-MFM25CDM) demonstrated a good fit to the Rasch model. Domain 1 was well targeted to the whole
severity spectrum—close mean locations for items and persons (0 vs 0.316)—whereas
domains 2 and 3 were better targeted to severe cases. The reliability coefficients
of the Rs-MFM25CDM suggested sufficient ability for each summed score to distinguish between patient
groups (0.9, 0.8, and 0.7 for domains 1, 2, and 3, respectively). A sufficient agreement
was found between results of the Rasch analysis and physical therapists' opinions.
Conclusions
The Rs-MFM25CDM can be considered a clinically relevant linear scale in each of its 3 domains and
may be soon reliably used for assessment in congenital disorders of the muscle.
Keywords
List of Abbreviations:
CM (congenital myopathy), CMD (congenital muscular dystrophy), DIF (differential item functioning), MFM (Motor Function Measure), Rs-MFM25CDM (Rasch-scaled MFM with 25 items for congenital disorders of the muscle)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: June 25, 2014
Footnotes
Supported by intramural funds of the National Institute of Neurological Disorders and Stroke, the Association Française contre les Myopathies, the Société Française de Médecine Physique et de Réadaptation, the Société Francophone d’Etude et de Recherche sur les Handicaps de l’Enfance, the Philippe Fundation, and Bouillat Terrier and Deage.
Disclosures: none.
Identification
Copyright
© 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
