Validity and reliability of the FSS in Greek MS patients

OBJECTIVES: The study provided validity and reliability evidence of the Fatigue Severity Scale (FSS) in Greek patients with multiple sclerosis (MS). MATERIALS AND METHODS: The FSS was administered to 72 MS patients, without co morbid fatigue and 75 matched paired controls with respect to gender and age. Both groups responded to the FSS, SF-36v2, BDI-II and a demographic questionnaire on two time points separated by a 1-week interval. Exploratory and confirmatory factor analysis was performed to test construct validity, concurrent and divergent validity, internal and test-retest reliability were also examined. RESULTS: Exploratory and confirmatory factor analysis, intercorrelations with BDI-II (r = 0.552, p < 0.01) and SF-36v2 vitality (r = −0.715, p < 0.01) and physical functioning (r = −0.673, p < 0.01) subscales, and differences between patients and non patients (t((145)) = 6.007, p < 0.001), revealed sufficient construct, concurrent and divergent validity evidence. The factor analysis demonstrated a unidimensional structure Cronbach alpha (0.953) and ICC (0.889) was high, indicating that the responses of our sample were internally consistent and stable across time. CONCLUSION: The Greek version of FSS is valid and reliable and may be used by clinicians and researchers to assess fatigue of Greek MS patients.