Verdam Mathilde G E, Oort Frans J, van der Linden Yvette M, Sprangers Mirjam A G
Department of Medical Psychology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands,
Qual Life Res. 2015 Mar;24(3):541-51. doi: 10.1007/s11136-014-0829-y. Epub 2014 Oct 18.
Missing data due to attrition present a challenge for the assessment and interpretation of change and response shift in HRQL outcomes. The objective was to handle such missingness and to assess response shift and 'true change' with the use of an attrition-based multigroup structural equation modeling (SEM) approach.
Functional limitations and health impairments were measured in 1,157 cancer patients, who were treated with palliative radiotherapy for painful bone metastases, before [time (T) 0], every week after treatment (T1 through T12), and then monthly for up to 2 years (T13 through T24). To handle missing data due to attrition, the SEM procedure was extended to a multigroup approach, in which we distinguished three groups: short survival (3-5 measurements), medium survival (6-12 measurements), and long survival (>12 measurements).
Attrition after third, sixth, and 13th measurement occasions was 11, 24, and 41 %, respectively. Results show that patterns of change in functional limitations and health impairments differ between patients with short, medium, or long survival. Moreover, three response-shift effects were detected: recalibration of 'pain' and 'sickness' and reprioritization of 'physical functioning.' If response-shift effects would not have been taken into account, functional limitations and health impairments would generally be underestimated across measurements.
The multigroup SEM approach enables the analysis of data from patients with different patterns of missing data due to attrition. This approach does not only allow for detection of response shift and assessment of true change across measurements, but also allow for detection of differences in response shift and true change across groups of patients with different attrition rates.
因失访导致的数据缺失给健康相关生活质量（HRQL）结果的变化评估及反应转移的解释带来了挑战。本研究的目的是处理此类数据缺失问题，并使用基于失访的多组结构方程模型（SEM）方法评估反应转移和“真实变化”。
对1157例因疼痛性骨转移接受姑息性放疗的癌症患者在治疗前[时间（T）0]、治疗后每周（T1至T12）以及之后长达2年每月（T13至T24）测量功能受限和健康损害情况。为处理因失访导致的数据缺失，将SEM程序扩展为多组方法，在此方法中我们区分了三组：短期生存（3 - 5次测量）、中期生存（6 - 12次测量）和长期生存（>12次测量）。
在第三次、第六次和第十三次测量时的失访率分别为11%、24%和41%。结果表明，短期、中期或长期生存患者的功能受限和健康损害变化模式不同。此外，检测到三种反应转移效应：“疼痛”和“疾病”的重新校准以及“身体功能”的重新排序。如果未考虑反应转移效应，各次测量中功能受限和健康损害通常会被低估。
多组SEM方法能够分析因失访导致具有不同数据缺失模式患者的数据。该方法不仅能够检测反应转移并评估各次测量中的真实变化，还能检测不同失访率患者组之间反应转移和真实变化的差异。
