Franco Franchignoni, Andrea Giordano, Gianpaolo Ronconi, Alessia Rabini, Giorgio Ferriero
Salvatore Maugeri Foundation, IRCCS, Scientific Institute of Veruno, IT-28010 Veruno (NO), Italy. E-mail: franco.franchignoni@fsm.it
DOI: 10.2340/16501977-1808

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.
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.