title: The AUSCAN subscales, AIMS-2 hand/finger subscale, and FIOHA were not unidimensional scales.
abstract: OBJECTIVE
  Evaluate the internal construct validity of the Australian/Canadian (AUSCAN) index for hand osteoarthritis (HOA) and identify the physical function instrument with best performance.
  
  
  METHODS
  AUSCAN, AIMS-2 (Arthritis Impact Measurement Scale 2), and Functional Index of HOA (FIHOA) were self-completed by 209 HOA patients (mean [standard deviation] age 61.6 [5.7] years) at baseline and 128 at follow-up. Rasch analysis was performed.
  
  
  RESULTS
  AUSCAN pain, physical function, and stiffness subscales comprised three constructs. AUSCAN scale performance was improved after removal of "Pain at rest" from the pain scale and division of physical function into two scales of high precision and grip strength tasks. AIMS-2 hand/finger subscale and FIHOA were improved after removal of one and two items, respectively and collapse of two AIMS-2 response categories. AUSCAN physical function scale showed better targeting to the sample and higher person reliability compared with FIHOA and especially AIMS-2 because of less "severe" items concerning grip strength tasks as opposed to precision tasks.
  
  
  CONCLUSIONS
  The AUSCAN subscales, AIMS-2 hand/finger scale, and FIHOA were not unidimensional. However, deletion of misfitting items improved scale performance. The revised AUSCAN physical function and FIHOA scales are preferable for measurement of grip strength and precision tasks, respectively.
authors.affiliation: Department of Rheumatology, Diakonhjemmet Hospital, PO Box 23 Vinderen, 0319 Oslo, Norway. ida.haugen@diakonsyk.no
authors.forename: Ida Kristin
authors.initials: IK
authors.lastname: Haugen
authors.forename: Rikke Helene
authors.initials: RH
authors.lastname: Moe
authors.forename: Barbara
authors.initials: B
authors.lastname: Slatkowsky-Christensen
authors.forename: Tore Kristian
authors.initials: TK
authors.lastname: Kvien
authors.forename: Désirée
authors.initials: D
authors.lastname: van der Heijde
authors.forename: Andrew
authors.initials: A
authors.lastname: Garratt
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D005260:Female; D006225:Hand / Q000503:physiopathology*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009664:Norway; D010003:Osteoarthritis / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology; D010147:Pain Measurement / Q000379:methods; D015203:Reproducibility of Results; D012720:Severity of Illness Index