Internal consistency, factor structure, and floor/ceiling effect of Quick Disabilities of the Arm, Shoulder, and Hand Questionnaire among people with carpal tunnel syndrome.

Quick Disability of the Arm, Shoulder, and Hand Questionnaire (QuickDASH) is commonly used in carpal tunnel syndrome, while the knowledge on its psychometrics in this disorder is limited. The objective of this study was to explore the internal consistency, factor structure, and floor/ceiling effect of QuickDASH among patients with carpal tunnel syndrome. This was a retrospective cross-sectional register-based study among 1597 patients with electromyography-confirmed carpal tunnel syndrome. The internal consistency was assessed using Cronbach's α . Exploratory factor analysis was used to evaluate factor structure. Of 1597 respondents, 896 (56%) were women. The average age was 55.0 (16.3) years. The mean QuickDASH score was 38 (23.2) points. QuickDASH demonstrated an excellent internal consistency with α of 0.92 (95% confidence interval: 0.92-0.93). Exploratory factor analysis demonstrated unidimensionality. Item loadings were moderate to substantial for all 11 items, varying from 0.55 to 0.83. A significant floor effect was observed for nine of 11 items varying from 20 to 51%. A ceiling effect was observed for one item (#6 'recreational activities'). Despite its significant floor effect, QuickDASH can be recommended as a valid and reliable scale to assess the severity of disability caused by carpal tunnel syndrome.