title: Can we scientifically and reliably measure the level of consciousness in vegetative and minimally conscious States? Rasch analysis of the coma recovery scale-revised.
abstract: OBJECTIVE
  (1) To appraise, by the means of Rasch analysis, the internal validity and reliability of the Coma Recovery Scale-Revised (CRS-R) in a sample of patients with disorder of consciousness (DOC); and (2) to provide information about the comparability of CRS-R scores across persons with DOC across different settings and groups, including different etiologies.
  
  
  METHODS
  Multicenter observational prospective study.
  
  
  METHODS
  Two rehabilitation wards, 1 intermediate care facility, and 2 nursing homes in Italy.
  
  
  METHODS
  Consecutively admitted patients (N=129) for which assessments at 2 different time points were available, giving a total sample of 258 observations.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  CRS-R.
  
  
  RESULTS
  After controlling for any possible dependency between persons' measures collected at different time points, and for uniform differential item functioning by etiology showed by the visual subscale, Rasch analysis demonstrated adequate satisfaction of all the model's requirements, including adequate ordering of scoring categories, unidimensionality, local independence, invariance (χ(2)21=27.798, P=.146), and absence of differential item functioning across patients' sex, age, time, and setting. The reliability (person separation index=.896) was adequate for individual person measurement. We devised a practical raw score to measure conversion tables based on the CRS-R calibrations.
  
  
  CONCLUSIONS
  The CRS-R is a psychometrically sound and robust measurement tool. The linear measures of ability derived from the CRS-R total scores do satisfy all the principles of scientific measurement and are sufficiently reliable for high stakes assessments, such as the diagnosis of the level of consciousness in individual patients. Future studies are needed to directly explore the capabilities of the CRS-R measures to reduce the risk of vegetative state misdiagnosis.
authors.affiliation: Rehabilitation Medicine Unit, Azienda Unità Sanitaria Locale Modena, Modena, Italy. fabiolaporta@mail.com
authors.forename: Fabio
authors.initials: F
authors.lastname: La Porta
authors.forename: Serena
authors.initials: S
authors.lastname: Caselli
authors.forename: Aladar Bruno
authors.initials: AB
authors.lastname: Ianes
authors.forename: Olivia
authors.initials: O
authors.lastname: Cameli
authors.forename: Mario
authors.initials: M
authors.lastname: Lino
authors.forename: Roberto
authors.initials: R
authors.lastname: Piperno
authors.forename: Antonella
authors.initials: A
authors.lastname: Sighinolfi
authors.forename: Francesco
authors.initials: F
authors.lastname: Lombardi
authors.forename: Alan
authors.initials: A
authors.lastname: Tennant
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003128:Coma / Q000503:physiopathology*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007380:Intermediate Care Facilities; D007558:Italy; D008297:Male; D008875:Middle Aged; D009735:Nursing Homes; D018458:Persistent Vegetative State / Q000503:physiopathology*; D011446:Prospective Studies; D011594:Psychometrics; D015203:Reproducibility of Results