Objective: The Fatigue Impact Scale for Daily Use (D-FIS) is an eight-item instrument designed to measure subjective daily experience of fatigue. This study sought to determine the metric properties of the D-FIS in multiple sclerosis (MS) patients.
Methods: Sixty-eight patients with operationally-defined MS and fatigue (54.8% of the sample) underwent the D-FIS. Usual clinical measures for MS, the Montgomery-Asberg Depression Rating Scale (MADRS) and the Functional Assessment of Multiple Sclerosis (FAMS) were also applied. In addition, patients with fatigue completed the Fatigue Descriptive Scale, the Multidimensional Fatigue Inventory (MFI), a Visual Analogue Scale for Fatigue (VAS-F), and a Global Perception of Fatigue Scale (GPF).
Results: Full computable data, 95.6%; both floor and ceiling effect=1.54%; item-total correlation=0.62 (item 1) to 0.84 (item 6); Cronbach's alpha=0.91; item homogeneity =0.55; standard error of measurement=3.18; convergent validity with other fatigue measures=-0.57 (VAS-F); 0.52 (GPF); and 0.46 (MFI-general fatigue). Test-retest reliability (ICC)=0.81. There was a strong association between health-related quality of life (HRQoL) (FAMS) and D-FIS (rS=0.70).
Conclusions: In this study, D-FIS proved to be a feasible and valid instrument for measuring MSrelated fatigue, a frequent symptom associated with deterioration of patients' HRQoL.