title: The structure of functional and community outcomes following traumatic brain injury.
abstract: OBJECTIVE
  To investigate the dimensionality of functional and community outcomes following serious TBI. To identify items that fit, misfit or are redundant, as well as to assess person misfit.
  
  
  METHODS
  Rating-scale (Rasch) analysis was applied to 1-year follow-up data from 231 cases in the US National TBI Model Systems database. Items selected for analysis included all items indicative of global outcomes, disability, activity or participation.
  
  
  RESULTS
  A powerful singular measurement dimension was identified. Item reliability was very high (0.98), as was person reliability (0.97). The dimension fit over 90% of cases; that is approximately 10% of cases displayed anomalous patterns of functioning that indicated that their functioning was not measurable in terms of the general dimension identified. There was tension within the dimension between ratings of dependency (FIM) and cognitive functioning in everyday life (NFI). Most-but not all-neuropsychological test scores misfit the outcome dimension.
  
  
  CONCLUSIONS
  Actual dimensionality was distinct from the named scales employed. A unidimensional measure model fit the data much better than expected. This outcome dimension might be called 'general community functioning'. In the future, it should be possible to develop more valid and parsimonious measures of community outcomes following TBI.
authors.affiliation: Kessler Medical Rehabilitation Research and Education Corporation, Department of Physical Medicine & Rehabilitation, University of Medicine and Dentistry of New Jersey/New Jersey Medical School, West Orange, NJ 07052, USA. mjohnston@kmrrec.org
authors.forename: Mark V
authors.initials: MV
authors.lastname: Johnston
authors.forename: Marla A
authors.initials: MA
authors.lastname: Shawaryn
authors.forename: James
authors.initials: J
authors.lastname: Malec
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Kreutzer
authors.forename: Flora M
authors.initials: FM
authors.lastname: Hammond
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D001930:Brain Injuries / Q000534:rehabilitation*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care / Q000379:methods / Q000592:standards*; D011594:Psychometrics; D015203:Reproducibility of Results; D016896:Treatment Outcome