Rasch Analysis of the QuickDASH in Patients with Neck Pain

<b>Background/Objectives</b>: 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. <b>Methods</b>: 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. <b>Results</b>: 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. <b>Conclusions</b>: 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.