Open AccessRasch analysis to evaluate the motor function measure for patients with facioscapulohumeral muscular dystrophy
Author(s) -
Karlien Mul,
Corinne G.C. Horlings,
Catharina G. Faber,
B.G.M. van Engelen,
Ingemar S. J. Merkies
Publication year - 2020
Publication title -
international journal of rehabilitation research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.452
H-Index - 52
eISSN - 1473-5660
pISSN - 0342-5282
DOI - 10.1097/mrr.0000000000000444
Subject(s) - rasch model , facioscapulohumeral muscular dystrophy , physical medicine and rehabilitation , ceiling effect , differential item functioning , polytomous rasch model , patient reported outcome , physical therapy , item response theory , psychology , sample size determination , scale (ratio) , measure (data warehouse) , audiology , medicine , muscular dystrophy , psychometrics , statistics , clinical psychology , developmental psychology , quality of life (healthcare) , data mining , computer science , pathology , mathematics , physics , alternative medicine , quantum mechanics , psychotherapist
Patient-relevant outcome measures for facioscapulohumeral muscular dystrophy (FSHD) are needed. The motor function measure (MFM) is an ordinal-based outcome measure for neuromuscular disorders, but its suitability to measure FSHD patients is questionable. Here, we performed Rasch analyses on MFM data from 194 FSHD patients to assess clinimetric properties in this patient group. Both the total scale and its three domains were analyzed (D1: standing position and transfers; D2: axial and proximal motor function; D3: distal motor function). Fit to the Rasch model, sample-item targeting, individual item fit, threshold ordering, sex- and age-based differential item functioning, response dependency and unidimensionality were assessed. Rasch analysis revealed multiple limitations of the MFM for FSHD, the most important being a large ceiling effect and suboptimal sample-item targeting, which were most pronounced for domains D2 and D3. There were disordered thresholds for most items, often resulting in items functioning in a dichotomous fashion. It was not possible to remodel the MFM into a Rasch-built interval scale. Remodeling of domain D1 into an interval scale with adequate fit statistics was achieved, but sample-item targeting remained suboptimal. Therefore, the MFM should be used with caution in FSHD patients, as it is not optimally suited to measure functional abilities in this patient group.