Article

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 alpha 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. CONCLUSION: 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.

Langue : ANGLAIS