Ryser L, Wright B D, Aeschlimann A, Mariacher-Gehler S, Stucki G
Ludwig-Maximilian University, Munich, Germany.
Arthritis Care Res. 1999 Oct;12(5):331-5. doi: 10.1002/1529-0131(199910)12:5<331::aid-art4>3.0.co;2-w.
The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a valid and widely used instrument for the assessment of osteoarthritis patients. We examined whether applying Rasch analysis, a new item-response theory, supports its metric properties.
The metric properties were examined in a cohort of patients with osteoarthritis of the hip or knee. In an exploratory approach, a validated German version of the WOMAC was analyzed using Rasch analysis for its unidimensionality and construct definition.
One hundred fifty-eight patients were included in the study. The 3 WOMAC domains--pain, stiffness, and physical function--were unidimensional when examined separately. In an analysis including all items, the stiffness items did not fit the model. This indicates that they are distinct from the pain and function items. Item difficulty analyses revealed redundancy between corresponding pain and function items addressing the same task (e.g., "pain while standing upright" and "difficulty while standing").
Applying Rasch analysis to the 3 WOMAC domains confirms their unidimensionality. However, the pain and function items seem to represent the same construct. Thus, it may be possible to simplify these domains to avoid redundancy. The impact of reducing items must nevertheless be examined.
西安大略和麦克马斯特大学骨关节炎指数（WOMAC）是一种用于评估骨关节炎患者的有效且广泛使用的工具。我们研究了应用新的项目反应理论——拉施分析是否支持其度量特性。
在一组髋部或膝部骨关节炎患者中检查其度量特性。采用探索性方法，使用拉施分析对经过验证的德文版WOMAC进行分析，以检验其单维度性和结构定义。
158名患者纳入研究。分别检查时，WOMAC的三个领域——疼痛、僵硬和身体功能——均为单维度。在包含所有项目的分析中，僵硬项目不符合模型。这表明它们与疼痛和功能项目不同。项目难度分析显示，处理相同任务的相应疼痛和功能项目之间存在冗余（例如，“直立时疼痛”和“站立困难”）。
对WOMAC的三个领域应用拉施分析证实了它们的单维度性。然而，疼痛和功能项目似乎代表相同的结构。因此，有可能简化这些领域以避免冗余。不过，必须检查减少项目的影响。
