Rasch validation of the Activities-specific Balance Confidence Scale and its short versions in
patients with Parkinson's disease
Sammanfattning
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 ? 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.