title: The Rivermead Mobility Index allows valid comparisons between subgroups of patients undergoing rehabilitation after stroke who differ with respect to age, sex, or side of lesion.
abstract: OBJECTIVE
  To investigate differential item functioning or item bias of the Rivermead Mobility Index (RMI) and its impact on the drawing of valid comparisons with the RMI between subgroups of patients after stroke who differ with respect to age, sex, or side of lesion.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  A rehabilitation center in the Netherlands and 2 stroke rehabilitation units and the wider community in the United Kingdom.
  
  
  METHODS
  The RMI was completed for patients undergoing rehabilitation after stroke (N=620; mean age ± SD, 69.2±12.5y; 297 [48%] men; 269 [43%] right hemisphere lesion, and 304 [49%] left hemisphere lesion).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Mokken scale analysis was used to investigate differential item functioning of the RMI between subgroups of patients who differed with respect to age (young vs older), sex (men vs women), and side of stroke lesion (right vs left hemisphere).
  
  
  RESULTS
  No differential item functioning was found for any of the comparison subgroups.
  
  
  CONCLUSIONS
  The RMI allows valid comparisons to be made between subgroups of patients undergoing rehabilitation after stroke who differ with respect to age, sex, or side of lesion.
authors.affiliation: Amsterdam Rehabilitation Research Center, Reade, Amsterdam, The Netherlands. l.roorda@reade.nl
authors.forename: Leo D
authors.initials: LD
authors.lastname: Roorda
authors.forename: John R
authors.initials: JR
authors.lastname: Green
authors.forename: Annemieke
authors.initials: A
authors.lastname: Houwink
authors.forename: Pam J
authors.initials: PJ
authors.lastname: Bagley
authors.forename: Jane
authors.initials: J
authors.lastname: Smith
authors.forename: Ivo W
authors.initials: IW
authors.lastname: Molenaar
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Geurts
mesh_terms: D000203:Activities of Daily Living; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D009426:Netherlands; D026741:Physical Therapy Modalities; D011379:Prognosis; D011594:Psychometrics; D020127:Recovery of Function / Q000502:physiology*; D012047:Rehabilitation Centers; D015203:Reproducibility of Results; D018570:Risk Assessment; D012720:Severity of Illness Index; D012737:Sex Factors; D020521:Stroke / Q000473:pathology*; D000071939:Stroke Rehabilitation; D016896:Treatment Outcome; D006113:United Kingdom