title: Rasch validation of the Activities-specific Balance Confidence Scale and its short versions in patients with Parkinson's disease.
abstract: OBJECTIVE
  To analyse in patients with Parkinson's disease the psychometric performance of the Activities-specific Balance Confidence scale (ABC) and its 3 short versions, using both a classical test theory approach and Rasch analysis.
  
  
  METHODS
  A sample of 217 patients with Parkinson's disease was assessed by ABC and the 3 short versions: Berg Balance Scale, Fear of Falling Measure, and the Unified Parkinson's Disease Rating Scale.
  
  
  RESULTS
  Cronbach's α was 0.95 in ABC, and ranged from 0.88 to 0.90 in its short versions. At Rasch analysis the 11 original rating categories were collapsed to 5 levels. In ABC 15 out of 16 items fitted the Rasch model. The ABC showed high correlation only with Fear of Falling Measure (r = 0.85), and excellent correlation with its short versions (r > 0.93). The 3 short versions showed a limited range of item difficulty estimates, low reliability levels, floor effect, a mismatch between mean item difficulty and mean ability of the patients.
  
  
  CONCLUSIONS
  In patients with Parkinson's disease: (i) the ABC has an adequate unidimensionality; (ii) the selection of its items is satisfactory, although there is room for some minor refinement; (iii) the 0-10 rating scale should be simplified, and a 5-level response format seems able to improve the measurement qualities of the scale; (iv) the 3 short versions showed some psychometric limitations in comparison with the ABC.
authors.affiliation: , Salvatore Maugeri Foundation, IRCCS, Scientific Institute of Veruno, IT-28010 Veruno (NO), Italy. franco.franchignoni@fsm.it, ffranchignoni@fsm.it.
authors.forename: Franco
authors.initials: F
authors.lastname: Franchignoni
authors.forename: Andrea
authors.initials: A
authors.lastname: Giordano
authors.forename: Gianpaolo
authors.initials: G
authors.lastname: Ronconi
authors.forename: Alessia
authors.initials: A
authors.lastname: Rabini
authors.forename: Giorgio
authors.initials: G
authors.lastname: Ferriero
mesh_terms: D000058:Accidental Falls; D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D005239:Fear; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology* / Q000523:psychology*; D004856:Postural Balance; D011594:Psychometrics; D015203:Reproducibility of Results