Ahmed Sara, Mayo Nancy E, Corbiere Marc, Wood-Dauphinee Sharon, Hanley James, Cohen Robin
Department of Epidemiology and Biostatistics, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.
Qual Life Res. 2005 Apr;14(3):611-27. doi: 10.1007/s11136-004-3708-0.
In many studies, assessments of change in self-report measures such as health-related quality of life must account for potential response shift, including reconceptualization and changes in internal standards of measurement.
The objective of our study was to compare healthy controls and individuals with stroke on the extent to which changes in internal standards and reconceptualization of health related quality of life (HRQL) occurs over the first 6 months post-stroke.
Confirmatory factor analysis was used to assess invariance of the SF-36 measurement model over time among 238 individuals with stroke and 392 controls, separately. This procedure assessed changes over time in the factor loadings, variances, and covariances of responses, and compared the extent of change between individuals with stroke and those in the control group. In addition a multisample comparison was made between individuals with stroke and members of the control group at the first evaluation in order to assess invariance of the SF-36 measurement model between the groups. The controls were considered to be a 'proxy' for the stroke cohort prior to the stroke.
We found no evidence of reconceptualization and changes in internal standards over time when the groups were assessed separately. There was a significant difference in the factor covariances (reconceptualization) between the two groups at the time of the first evaluation. However, measurement error was also significant for this comparison.
This study indicates that the improvement in HRQL over time is real rather than a result of reconceptualization or a recalibration. If response shift does occur with stroke it is likely to be mediated by the event itself and not the recovery process.
在许多研究中，对诸如健康相关生活质量等自我报告测量指标变化的评估必须考虑潜在的反应偏移，包括重新概念化和测量内部标准的变化。
我们研究的目的是比较健康对照组和中风患者在中风后最初6个月内健康相关生活质量（HRQL）的内部标准变化和重新概念化的程度。
分别对238名中风患者和392名对照组进行验证性因素分析，以评估SF-36测量模型随时间的不变性。该程序评估了反应的因素负荷、方差和协方差随时间的变化，并比较了中风患者和对照组之间的变化程度。此外，在首次评估时对中风患者和对照组成员进行了多样本比较，以评估SF-36测量模型在两组之间的不变性。对照组被视为中风队列中风前的“替代”。
当分别评估两组时，我们没有发现随时间重新概念化和内部标准变化的证据。在首次评估时，两组之间的因素协方差（重新概念化）存在显著差异。然而，这种比较的测量误差也很显著。
本研究表明，HRQL随时间的改善是真实的，而不是重新概念化或重新校准的结果。如果中风确实发生反应偏移，很可能是由事件本身介导的，而不是恢复过程。
