Rasch Analysis of the QuickDASH in Patients with Neck Pain.

Background/Objectives: Many patients with neck pain have arm problems. The purpose of this study was to examine the psychometric properties of the QuickDASH in patients reporting neck pain by Rasch analysis. Methods: The study was a cross-sectional study. Rasch analysis was used to examine the QuickDASH for unidimensionality, category function, item difficulty and targeting, and reliability in patients with neck pain. The two-factor model, comprising a function factor (items 1-8) and symptom factor (items 9-11), were separately assessed by Rasch analysis. Results: The mean age of the 302 participants was 57.9 ± 10.4 years old. The mean QuickDASH score was 24.8 ± 23.3 (95% CI: 22.2-27.5). For the function factor, the InfitMNSQ/OutfitMNSQ ranges were 0.700-1.124/0.661-1.121, indicating that all items fitted the model's expectation. Only two items (items 4 and 6) exhibited category response disorder. The map for the person-item response thresholds covered the patient distribution well. The reliability was good, with a person separation index of 0.85. For the symptom factor, the InfitMNSQ/OutfitMNSQ ranges were 0.522-0.863/0.517-0.885, indicating that all items fitted the model's expectation. No items with category response disorder were found for the symptom factor, and the reliability was good, with a person separation index of 0.82. Conclusions: The items fit the Rasch model well, and the wide range of item response thresholds covered the ranges of the patients' disability and symptoms well. The QuickDASH has a two-factor structure, and is an excellent measure of upper limb function and symptoms in patients reporting neck pain.