title: Evidence of multidimensionality in the ALSFRS-R Scale: a critical appraisal on its measurement properties using Rasch analysis.
abstract: OBJECTIVE
  To examine dimensionality, reliability and validity of the Amyotrophic Lateral Sclerosis Functional Rating Scale-revised (ALSFRS-R) using traditional classical test theory methods and Rasch analysis in order to provide a rationale for possible improvement of its metric quality.
  
  
  METHODS
  Methodological research on ALSFRS-R collected in a consecutive sample of 485 patients with amyotrophic lateral sclerosis (ALS) attending three tertiary ALS centres.
  
  
  RESULTS
  The ALSFRS-R items showed good internal consistency but dimensionality analysis argues against the use of ALSFRS-R as a single score because the scale lacks unidimensionality. Parallel analysis and exploratory factor analysis revealed three factors representing the following domains: (1) bulbar function; (2) fine and gross motor function; and (3) respiratory function. Rasch analysis showed that all items in each domain fitted the respective constructs to measure, except for item No 9 'climbing stairs' and item No 12 'respiratory insufficiency'. Rating categories did not comply with the criteria for category functioning. Collapsing the scale's 5 level ratings into 3 levels improved its metric quality.
  
  
  CONCLUSIONS
  The ALSFRS-R fails to satisfy rigorous measurement standards and should be, at least in part, revised. At present, ALSFRS-R should be considered as a profile of mean scores from three different domains (bulbar, motor and respiratory functions) more than a global total score. Further studies on ALSFRS-R using modern psychometric methods are warranted to confirm our findings and refine the metric quality of this scale, through a step by step process.
authors.affiliation: Unit of Occupational Rehabilitation and Ergonomics, Fondazione Salvatore Maugeri, Scientific Institute of Veruno, , Novara, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Franchignoni
authors.forename: Gabriele
authors.initials: G
authors.lastname: Mora
authors.forename: Andrea
authors.initials: A
authors.lastname: Giordano
authors.forename: Paolo
authors.initials: P
authors.lastname: Volanti
authors.forename: Adriano
authors.initials: A
authors.lastname: Chiò
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011237:Predictive Value of Tests; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index
keywords: ALS