Dencker Anna, Sunnerhagen Katharina S, Taft Charles, Lundgren-Nilsson Åsa
Centre for Person-centred Care, Institute of Health and Care Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
Institute of Health and Care Sciences, Sahlgrenska Academy, University of Gothenburg, Box 457, 405 30, Gothenburg, Sweden.
Health Qual Life Outcomes. 2015 Feb 12;13:20. doi: 10.1186/s12955-015-0213-9.
Fatigue is a common symptom in post-polio syndrome (PPS) and can have a substantial impact on patients. There is a need for validated questionnaires to assess fatigue in PPS for use in clinical practice and research. The aim with this study was to assess the validity and reliability of the Swedish version of Multidimensional Fatigue Inventory (MFI-20) in patients with PPS using the Rasch model.
A total of 231 patients diagnosed with PPS completed the Swedish MFI-20 questionnaire at post-polio out-patient clinics in Sweden. The mean age of participants was 62 years and 61% were females. Data were tested against assumptions of the Rasch measurement model (i.e. unidimensionality of the scale, good item fit, independency of items and absence of differential item functioning). Reliability was tested with the person separation index (PSI). A transformation of the ordinal total scale scores into an interval scale for use in parametric analysis was performed. Dummy cases with minimum and maximum scoring were used for the transformation table to achieve interval scores between 20 and 100, which are comprehensive limits for the MFI-20 scale.
An initial Rasch analysis of the full scale with 20 items showed misfit to the Rasch model (p < 0.001). Seven items showed slightly disordered thresholds and person estimates were not significantly improved by rescoring items. Analysis of MFI-20 scale with the 5 MFI-20 subscales as testlets showed good fit with a non-significant x (2) value (p = 0.089). PSI for the testlet solution was 0.86. Local dependency was present in all subscales and fit to the Rasch model was solved with testlets within each subscale. PSI ranged from 0.52 to 0.82 in the subscales.
This study shows that the Swedish MFI-20 total scale and subscale scores yield valid and reliable measures of fatigue in persons with post-polio syndrome. The Rasch transformed total scores can be used for parametric statistical analyses in future clinical studies.
疲劳是小儿麻痹后遗症（PPS）的常见症状，会对患者产生重大影响。在临床实践和研究中，需要经过验证的问卷来评估PPS患者的疲劳情况。本研究旨在使用Rasch模型评估瑞典版多维疲劳量表（MFI - 20）在PPS患者中的有效性和可靠性。
共有231名被诊断为PPS的患者在瑞典的小儿麻痹后遗症门诊完成了瑞典语版的MFI - 20问卷。参与者的平均年龄为62岁，61%为女性。数据根据Rasch测量模型的假设进行检验（即量表的单维度性、良好的项目拟合度、项目独立性以及不存在项目功能差异）。使用人员分离指数（PSI）测试信度。将有序的总分转化为区间量表以用于参数分析。使用最低分和最高分的虚拟案例来制作转换表，以获得20至100之间的区间分数，这是MFI - 20量表的综合范围。
对包含20个项目的完整量表进行的初始Rasch分析显示与Rasch模型不拟合（p < 0.001）。7个项目显示阈值略有紊乱，重新计分后人员估计没有显著改善。将MFI - 20量表的5个分量表作为测试单元进行分析，显示拟合良好，x（2）值不显著（p = 0.089）。测试单元解决方案的PSI为0.86。所有分量表中都存在局部依赖性，通过每个分量表内的测试单元解决了与Rasch模型的拟合问题。分量表中的PSI范围为0.52至0.82。
本研究表明，瑞典语版MFI - 20的总量表和分量表得分能够有效且可靠地测量小儿麻痹后遗症患者的疲劳情况。Rasch转换后的总分可用于未来临床研究中的参数统计分析。
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