title: Psychometric evaluation of the myasthenia gravis composite using Rasch analysis.
abstract: BACKGROUND
  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.
authors.affiliation: Department of Neurology, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Sadjadi
authors.forename: Mark
authors.initials: M
authors.lastname: Conaway
authors.forename: Gary
authors.initials: G
authors.lastname: Cutter
authors.forename: Donald B
authors.initials: DB
authors.lastname: Sanders
authors.forename: Ted M
authors.initials: TM
authors.lastname: Burns
mesh_terms: D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000175:diagnosis* / Q000503:physiopathology; D017063:Outcome Assessment, Health Care; D011594:Psychometrics; D012189:Retrospective Studies; D012720:Severity of Illness Index