Abstract
Fatigue is one of the most frequent complaints of patients with multiple sclerosis (MS). The Fatigue Impact Scale (FIS), one of the 30 available fatigue questionnaires, is commonly applied because it evaluates multidimensional aspects of fatigue. The chief objectives of this study were to validate FIS and evaluate the psychometric properties of MS patients in Serbia. One hundred and twenty-one (121) MS patients and one hundred and twenty-two (122) age-, gender- and education-matched healthy control (HC) subjects completed the FIS and the Beck Depression Inventory. Internal consistency of the FIS subscales was determined using Cronbach's Alpha Coefficient. Test/retest reliability with an intra-class correlation coefficient (ICC) for each FIS subscale was performed. The total FIS score and subscale scores showed statistically significant differences between the MS patients and the HC subjects in both FIS sessions. Cronbach's Alpha was 0.966. All ICCs were statistically significant (p < 0.05). The Serbian version of this instrument may be useful as a clinical measure for fatigue and functionality in patients with MS.