title: Factor structure of Guy's Neurological Disability Scale in a sample of Dutch patients with multiple sclerosis.
abstract: BACKGROUND
  Guy's Neurological Disability Scale (GNDS) is designed to assess disability (i.e. activity limitations) in patients with multiple sclerosis. It contains 12 functional domains, each indicating a level of disability. Four domain scores and a total score can be calculated.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the structural validity of the GNDS in a Dutch population who were definitely diagnosed as having multiple sclerosis.
  
  
  METHODS
  Data of 974 patients were available. The structural validity of the GNDS was evaluated by confirmatory item factor analysis (CIFA). Two first-order models and two bifactor models were investigated.
  
  
  RESULTS
  The best fitted model was a bifactor model with a general factor underlying all items, and 10 items loading on 3 group factors. Cronbach's alpha on the general factor (0.78) and on the group factor spinal-plus (0.74) were satisfying. Cronbach's alpha on the group factors mental (0.56) and bulbar (0.48) were low. Reliability based on CIFA was 0.85.
  
  
  CONCLUSIONS
  Results showed a clear factor structure of the GNDS. It justifies the use of the total score of the GNDS. In addition, three sub-scale scores could be used.
authors.affiliation: Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands. w.mokkink@vumc.nl
authors.forename: L B
authors.initials: LB
authors.lastname: Mokkink
authors.forename: D L
authors.initials: DL
authors.lastname: Knol
authors.forename: B M J
authors.initials: BM
authors.lastname: Uitdehaag
mesh_terms: D004185:Disability Evaluation; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D009103:Multiple Sclerosis / Q000145:classification / Q000175:diagnosis*; D009420:Nervous System / Q000503:physiopathology; D009426:Netherlands; D009460:Neurologic Examination; D012720:Severity of Illness Index