Validity, factor structure, and clinical relevance of the AUSCAN Osteoarthritis Hand Index

Objective. The Australian/Canadian (AUSCAN) Osteoarthritis Hand Index is a self-report assessment of pain, stiffness, and function in patients with hand osteoarthritis (OA). Small studies have confirmed the reliability, construct validity, and responsiveness of this measure, but the factor structure has not been examined. In this study, we examined the clinimetric properties and clinical relevance of the AUSCAN index in a large sample of patients with familial hand OA. Methods. The study group comprised 700 patients (80% female, mean age 69 years) who were part of a study on the genetics of generalized OA. All patients had radiographic hand OA bilaterally. The analyses examined internal consistency, factor structure, and relationships of the subscales to grip and pinch strength and a single-item pain measure. Results. Internal consistency was high for the total AUSCAN index and the subscales (Cronbach's alpha = 0.93-0.96). The AUSCAN function subscale had the strongest correlation with grip and pinch strength, and the pain subscale had the strongest correlation with the single-item pain measure, thus supporting the construct validity of these subscales. Factor analysis showed that all pain and function items clearly loaded on the subscale they were intended to measure. Each 1-unit increase in the AUSCAN function subscale was associated with a clinically relevant decrease in hand strength. Conclusion. The results of this study strongly confirm the clinimetric properties of the AUSCAN index, including the validity of specific subscales. Results indicate that the AUSCAN index can measure meaningful changes in pain, stiffness, and function.