Validation of a manual ability questionnaire in patients with systemic sclerosis.

Objective: To adapt and validate a manual ability questionnaire, the ABILHAND, developed through the Rasch methodology in patients with systemic sclerosis (SSc).
Methods: The original version of the ABILHAND, which includes 81 manual daily activities, was presented to 156 patients with SSc. They were asked to provide their perceived difficulty in performing each manual activity on a 3-level scale: impossible, difficult, or easy. Items were selected from well-established psychometric criteria. The patients were reassessed 1 month later to test the reproducibility. Concomitantly, they were clinically evaluated for their disease activity/severity, and their functional ability was tested with the Health Assessment Questionnaire (HAQ).
Results: The 26 selected items defined a unidimensional and linear measure of manual ability and showed a continuous progression in their difficulty. The item difficulty hierarchy was invariant across 12 patient-related factors and the manual ability score was reproducible over time. Finally, the manual ability was significantly poorer in SSc patients with more severe disease, and was negatively correlated with the HAQ score (rho = -0.733).
Conclusion: The SSc-adapted ABILHAND questionnaire is a reliable, valid, reproducible, linear, and unidimensional measure to assess and followup on the manual ability of patients with SSc; therefore, it could become a useful additional tool in clinical trials to assess treatment efficacy.