OBJECTIVE: Primary Sjogren's syndrome (SS) is an autoimmune disease characterized by fatigue. Little is known about the genesis of fatigue. Fatigue is thought to represent a multidimensional concept and it is important to be able to measure it confidently. The aims were to evaluate the reliability and validity of the 20-item Multidimensional Fatigue Inventory (MFI-20) in SS and to search for factors associated with this disabling symptom.
METHODS: Forty-eight women with primary SS completed the MFI-20 questionnaire. The results were compared with age-matched women with fibromyalgia (FM) and healthy controls. Convergent construct validity was assessed by correlations to a Visual Analogue Scale (VAS) for global fatigue by Spearman's correlation (r(s)). Test-retest reliability was analysed by the intraclass correlation coefficient (ICC) in 28 women. Associations between clinical variables and subscales of the MFI-20 were analysed.
RESULTS: The SS women scored significantly higher in all subscales of the MFI-20 compared to controls but similar to FM. The ICCs were satisfactory, ranging from 0.66 for general fatigue to 0.85 for the total score of MFI-20. All subscales correlated significantly to VAS for global fatigue, general fatigue showing the highest correlation (r(s) = 0.70). The estimated number of hours of sleep/day was significantly associated with many of the fatigue dimensions. All five subscales of the MFI-20 were inversely associated with diastolic blood pressure (BP) and two with systolic BP.
CONCLUSIONS: The MFI-20 was found to be a reliable and valid tool for the measurement of fatigue in primary SS. High levels of fatigue were correlated with low BP, suggesting an associated involvement of the autonomic nervous system.
2008. Vol. 37, no 4, 284-292 p.