Deng Nina, Anatchkova Milena D, Waring Molly E, Han Kyung T, Ware John E
Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, MA, 01655, USA,
Qual Life Res. 2015 Aug;24(8):1809-22. doi: 10.1007/s11136-015-0916-8. Epub 2015 Jan 20.
The Quality-of-life (QOL) Disease Impact Scale (QDIS(®)) standardizes the content and scoring of QOL impact attributed to different diseases using item response theory (IRT). This study examined the IRT invariance of the QDIS-standardized IRT parameters in an independent sample.
The differential functioning of items and test (DFIT) of a static short-form (QDIS-7) was examined across two independent sources: patients hospitalized for acute coronary syndrome (ACS) in the TRACE-CORE study (N = 1,544) and chronically ill US adults in the QDIS standardization sample. "ACS-specific" IRT item parameters were calibrated and linearly transformed to compare to "standardized" IRT item parameters. Differences in IRT model-expected item, scale and theta scores were examined. The DFIT results were also compared in a standard logistic regression differential item functioning analysis.
Item parameters estimated in the ACS sample showed lower discrimination parameters than the standardized discrimination parameters, but only small differences were found for thresholds parameters. In DFIT, results on the non-compensatory differential item functioning index (range 0.005-0.074) were all below the threshold of 0.096. Item differences were further canceled out at the scale level. IRT-based theta scores for ACS patients using standardized and ACS-specific item parameters were highly correlated (r = 0.995, root-mean-square difference = 0.09). Using standardized item parameters, ACS patients scored one-half standard deviation higher (indicating greater QOL impact) compared to chronically ill adults in the standardization sample.
The study showed sufficient IRT invariance to warrant the use of standardized IRT scoring of QDIS-7 for studies comparing the QOL impact attributed to acute coronary disease and other chronic conditions.
生活质量（QOL）疾病影响量表（QDIS(®)）使用项目反应理论（IRT）对不同疾病所致生活质量影响的内容和评分进行标准化。本研究在一个独立样本中检验了QDIS标准化IRT参数的IRT不变性。
在两个独立来源中检验了静态简表（QDIS-7）的项目和测验的差异功能（DFIT）：TRACE-CORE研究中因急性冠状动脉综合征（ACS）住院的患者（N = 1,544）以及QDIS标准化样本中的美国慢性病成年人。校准“ACS特异性”IRT项目参数并进行线性变换，以与“标准化”IRT项目参数进行比较。检验了IRT模型预期的项目、量表和θ分数的差异。还在标准逻辑回归差异项目功能分析中比较了DFIT结果。
在ACS样本中估计的项目参数显示出比标准化区分参数更低的区分参数，但在阈值参数方面仅发现了微小差异。在DFIT中，非补偿性差异项目功能指数的结果（范围为0.005 - 0.074）均低于0.096的阈值。在量表水平上，项目差异进一步被消除。使用标准化和ACS特异性项目参数的ACS患者基于IRT的θ分数高度相关（r = 0.995，均方根差异 = 0.09）。与标准化样本中的慢性病成年人相比，使用标准化项目参数时，ACS患者的得分高出半个标准差（表明对生活质量的影响更大）。
该研究表明有足够的IRT不变性，足以保证在比较急性冠状动脉疾病和其他慢性疾病所致生活质量影响的研究中使用QDIS-7的标准化IRT评分。
