Twiss J, McKenna S P
Galen Research Ltd, Enterprise House, Manchester Science Park, Lloyd Street North, Manchester, M15 6SE, UK,
Qual Life Res. 2015 Jan;24(1):105-13. doi: 10.1007/s11136-014-0630-y. Epub 2014 Jan 30.
Disease-specific patient-reported outcome (PRO) measures are designed to be highly relevant to one disease. It is widely believed that comparisons of outcomes between patients with different diseases are only possible using generic measures. The present study employs a novel method of using Rasch analysis to co-calibrate scores from different disease-specific PRO measures, allowing scores to be compared across diseases.
Psoriasis patients (n = 146, mean age = 44.4, males = 50 %) completed the Psoriasis Quality of Life scale (PSORIQoL) and atopic dermatitis patients (n = 146, mean age = 45.5, males = 50 %) the Quality of Life in Atopic Dermatitis scale (QoLIAD). Both measures employ the needs-based model of QoL, and they share five common items-providing a link between assessments. The groups were analysed separately, and then combined to test fit to the Rasch model.
Both scales showed good fit to the Rasch model after minor adjustments (PSORIQoL: χ (2) p = 0.25; QoLIAD: χ (2) p = 0.51). For the combined dataset, one common item showing differential item functioning by disease was removed and fit to the Rasch model was achieved (χ (2) p = 0.08). The co-calibrated scale successfully distinguished between perceived severity groups (p < 0.001).
It is possible to co-calibrate scores on the PSORIQoL and QoLIAD. This is one of the first studies in health research to demonstrate how Rasch analysis can be used to make comparisons across diseases using different disease-specific measures. Such an approach maintains the greater relevance and, consequently, accuracy associated with disease-specific measurement.
特定疾病患者报告结局（PRO）指标旨在与某一种疾病高度相关。人们普遍认为，只有使用通用指标才能对不同疾病患者的结局进行比较。本研究采用了一种新方法，即使用拉施分析对来自不同特定疾病PRO指标的分数进行共同校准，从而能够对不同疾病的分数进行比较。
银屑病患者（n = 146，平均年龄 = 44.4岁，男性占50%）完成了银屑病生活质量量表（PSORIQoL），特应性皮炎患者（n = 146，平均年龄 = 45.5岁，男性占50%）完成了特应性皮炎生活质量量表（QoLIAD）。这两个指标均采用基于需求的生活质量模型，且有五个共同项目——这为评估之间提供了联系。对两组分别进行分析，然后合并以检验是否符合拉施模型。
经过 minor adjustments后，两个量表均显示出与拉施模型的良好拟合度（PSORIQoL：χ(2)p = 0.25；QoLIAD：χ(2)p = 0.51）。对于合并后的数据集，去除了一个显示出因疾病而异的项目功能差异的共同项目，并实现了与拉施模型的拟合（χ(2)p = 0.08）。共同校准后的量表成功区分了感知严重程度组（p < 0.001）。
可以对PSORIQoL和QoLIAD的分数进行共同校准。这是健康研究中首批证明如何使用拉施分析通过不同的特定疾病指标对不同疾病进行比较的研究之一。这种方法保持了与特定疾病测量相关的更高相关性，从而提高了准确性。
