MEASURING THE FUNCTIONAL IMPACT OF FATIGUE - INITIAL VALIDATION OF THE FATIGUE IMPACT SCALE

The fatigue impact scale (FIS) was developed to improve our understand ing of the effects of fatigue on quality of life. The FIS examines pat ients' perceptions of the functional limitations that fatigue has caus ed over the past month. FIS items reflect perceived impact on cognitiv e, physical, and psychosocial functioning. This study compared 145 pat ients referred for investigation of chronic fatigue (ChF) with 105 pat ients with multiple sclerosis (MS) and 34 patients with mild hypertens ion (HT). Internal consistency for the FIS and its three subscales was > .87 for all analyses. Fatigue impact was highest for the ChF group although the MS group's reported fatigue also exceeded that of the HT group. Discriminant function analysis correctly classified 80.0% of th e ChF group and 78.1% of the MS group when these groups were compared. This initial validation study indicates that the FIS has considerable merit as a measure of patients' attribution of functional limitations to symptoms of fatigue.