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Psychometric evaluation of the myasthenia gravis composite using rasch analysis
Author(s) -
Sadjadi Reza,
Conaway Mark,
Cutter Gary,
Sanders Donald B.,
Burns Ted M.
Publication year - 2012
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.23260
Subject(s) - rasch model , myasthenia gravis , item response theory , psychometrics , differential item functioning , physical therapy , medicine , psychology , audiology , clinical psychology , statistics , mathematics , developmental psychology
: The MG Composite (MGC) is a validated outcome measure of the clinical manifestations of myasthenia gravis. Methods : We performed Rasch analyses of the MGC to investigate additional properties, including its unidimensionality and the appropriateness of the weights assigned to the response categories for the MGC items. Results : The fit statistics indicated that the 10 items belong together and can be summated for a total score. There was an overall absence of item order distortion between response categories. The Rasch model's expected category response values were compatible with item weights previously assigned. Conclusions : Our analysis suggests that: (1) the score can be summated to estimate an overall disease severity score; (2) the response options of the 10 items are not significantly distorted; and (3) the assigned weights of the response options are appropriate. Muscle Nerve 45: 820–825, 2012