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Research paper
Evidence of multidimensionality in the ALSFRS-R Scale: a critical appraisal on its measurement properties using Rasch analysis
  1. Franco Franchignoni1,
  2. Gabriele Mora2,
  3. Andrea Giordano3,
  4. Paolo Volanti4,
  5. Adriano Chiò5
  1. 1Unit of Occupational Rehabilitation and Ergonomics, Fondazione Salvatore Maugeri, Scientific Institute of Veruno, Novara, Italy
  2. 2Department of Neurorehabilitation, ALS Centre, Fondazione Salvatore Maugeri, Scientific Institute of Milano, Milano, Italy
  3. 3Service of Bioengineering, Fondazione Salvatore Maugeri, Scientific Institute of Veruno, Novara, Italy
  4. 4Department of Neurorehabilitation, ALS Centre, Fondazione Salvatore Maugeri, Scientific Institute of Mistretta, Messina, Italy
  5. 5Department of Neuroscience, ALS Centre, University of Torino and Azienda Ospedaliera Città della Salute e della Scienza, Torino, Italy
  1. Correspondence to Professor A Chiò, Department of Neuroscience, University of Torino, ALS Centre, Via Cherasco 15, Torino 10126, Italy; achio{at}usa.net

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.

  • ALS

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