National School of Public Health and CIBERNED, Carlos III Institute of Health, Madrid, Spain.
Eur J Neurol. 2010 Feb;17(2):202-7. doi: 10.1111/j.1468-1331.2009.02791.x. Epub 2009 Oct 14.
The SCales for Outcomes in PArkinson's disease-Cognition (SCOPA-COG) is a specific measure of cognitive function for Parkinson's disease (PD) patients. Previous studies, under the frame of the classic test theory, indicate satisfactory psychometric properties. The Rasch model, an item response theory approach, provides new information about the scale, as well as results in a linear scale. This study aims at analysing the SCOPA-COG according to the Rasch model and, on the basis of results, suggesting modification to the SCOPA-COG.
Fit to the Rasch model was analysed using a sample of 384 PD patients.
A good fit was obtained after rescoring for disordered thresholds. The person separation index, a reliability measure, was 0.83. Differential item functioning was observed by age for three items and by gender for one item.
The SCOPA-COG is a unidimensional measure of global cognitive function in PD patients, with good scale targeting and no empirical evidence for use of the subscale scores. Its adequate reliability and internal construct validity were supported. The SCOPA-COG, with the proposed scoring scheme, generates true linear interval scores.
SCales for Outcomes in PArkinson's disease-Cognition（SCOPA-COG）是帕金森病（PD）患者认知功能的特定测量工具。先前的研究表明，在经典测试理论的框架下，该工具具有令人满意的心理计量学特性。项目反应理论方法——Rasch 模型，为量表提供了新的信息，并产生了线性量表。本研究旨在根据 Rasch 模型对 SCOPA-COG 进行分析，并根据结果提出对 SCOPA-COG 的修改建议。
使用 384 名 PD 患者的样本对 Rasch 模型进行拟合分析。
经过阈值紊乱校正后，拟合效果良好。个体分离指数，一种可靠性度量，为 0.83。三个项目存在年龄差异，一个项目存在性别差异。
SCOPA-COG 是 PD 患者整体认知功能的一个维度测量工具，具有良好的量表目标定位，没有使用子量表得分的经验证据。它的可靠性和内部结构效度得到了支持。SCOPA-COG 采用了建议的评分方案，生成了真正的线性区间分数。
