Department of Human and Social Sciences, University of Aosta Valley, Aosta, Italy.
Department of Psychology, University of Turin, Turin, Italy.
Health Qual Life Outcomes. 2021 Jan 6;19(1):9. doi: 10.1186/s12955-020-01663-y.
Response shift (RS) has been defined as a change in the meaning of an individual's self-evaluation that needs to be accounted for when assessing longitudinal changes in health-related quality of life (HRQoL). RS detection through structural equation modeling is accomplished by adopting Oort's procedure based on a measurement model in which the observed variables are defined as reflective indicators of the HRQoL latent variable; that is, the latent variable causes the variation in the reflective indicators. This study aims to propose a procedure that assesses RS when formative indicators are used in measuring HRQoL; in this last case, the latent variable is considered to be a function of some formative indicators. A secondary aim is to compare the new procedure with Oort's procedure to highlight similarities and differences.
The data were retrieved from a consecutive series of 258 patients newly diagnosed with colorectal cancer and undergoing chemotherapy and/or surgery. The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QOL-C30) was administered twice, once before and once six months after treatment. Structural equation modeling was used to evaluate RS and true change with the newly proposed method (in which fatigue and pain were defined as formative indicators) and with Oort's procedure (in which fatigue and pain were defined as reflective indicators).
According to the new procedure, there was no measurement bias, and on average, patients' quality of life improved by 3.53 points (on a scale ranging from 0 to 100) at the 6-month follow-up. With Oort's procedure, the loading of the pain indicator was not invariant across the two time points, suggesting the presence of reprioritization, whereas the estimation of true change was very similar to the previous one: 3.87.
RS and true change in HRQoL can be evaluated in the presence of formative indicators. Defining a measurement model by formative or reflective indicators can lead to different results.
反应转移（RS）被定义为个体自我评估的意义发生变化，在评估健康相关生活质量（HRQoL）的纵向变化时需要考虑到这一点。通过采用 Oort 基于测量模型的程序进行结构方程建模，可以实现 RS 的检测，在该模型中，观察变量被定义为 HRQoL 潜在变量的反射指标；也就是说，潜在变量导致反射指标的变化。本研究旨在提出一种在使用形成性指标测量 HRQoL 时评估 RS 的程序；在后一种情况下，潜在变量被认为是一些形成性指标的函数。次要目的是比较新程序和 Oort 程序，以突出异同。
数据来自连续的 258 例新诊断为结直肠癌并接受化疗和/或手术的患者系列。欧洲癌症研究与治疗组织（EORTC）生活质量问卷（EORTC QOL-C30）在治疗前和治疗后 6 个月各进行了一次测量。使用结构方程建模来评估新提出的方法（其中疲劳和疼痛被定义为形成性指标）和 Oort 程序（其中疲劳和疼痛被定义为反射性指标）中的 RS 和真实变化。
根据新程序，不存在测量偏差，平均而言，患者的生活质量在 6 个月随访时提高了 3.53 分（在 0 到 100 的范围内）。使用 Oort 程序，疼痛指标的负荷在两个时间点上没有不变性，表明存在重新优先化，而真实变化的估计与之前非常相似：3.87。
在存在形成性指标的情况下，可以评估 HRQoL 的 RS 和真实变化。通过形成性或反射性指标定义测量模型可能会导致不同的结果。
