Assessment of fatigue in patients with fibromyalgia and chronic widespread pain. Reliability and validity of the Swedish version of the MFI-20.
Department of Rheumatology and Inflammation Research, Sahlgrenska Academy, Göteborg University, Göteborg, Sweden.
Objectives. Fibromyalgia (FM) and Chronic Widespread Pain (CWP) are common diseases in primary care and, in addition to the pain they cause, fatigue is a major problem. Fatigue is regarded as a multidimensional concept and instruments assessing fatigue should therefore cover several different dimensions. The Multidimensional Fatigue Inventory (MFI-20) measures five different dimensions of fatigue. The aim of the study was to investigate the test-retest reliability and convergent construct validity of the Swedish version of the MFI-20 in female patients with FM or CWP. Methods. To investigate the convergent construct validity, 166 female patients with FM or CWP completed the Swedish version of the MFI-20 and a Visual Analogue Scale (VAS) measuring global fatigue. Thirty-six of the 166 patients completed the Swedish version of the MFI-20 on two occasions, one day apart to evaluate the test-retest reliability. Results. Spearman's correlation coefficient revealed a significant association between each of the five subscales of the MFI-20 and the VAS for global fatigue. General Fatigue had the highest correlation with the VAS (rs = 0.62, p<0.001), while Reduced Motivation had the lowest (rs = 0.32, p<0.001). The intra-class correlation coefficients (ICC) were satisfactory for all the five subscales of the MFI-20. Conclusion. The results of this study indicate that the Swedish version of the MFI-20 is a reliable tool for assessing the degree of fatigue in patients with FM or CWP. This study also supports the theory that fatigue is a multidimensional concept and different aspects of fatigue should be measured separately.
PMID: 17852297 [PubMed - as supplied by publisher]
