Psychometric study of Turkish version of Fatigue Impact Scale in multiple sclerosis patients

Abstract

Background: The aims of this study were to test the validity, test-retest reliability, and internal consistency of Turkish version of FIS; the variables affecting FIS score.

Materials and methods: 71 MS patients and 68 healthy subjects were included to the study.

Results: Total FIS score and subscale scores were different statistically between MS patients and healthy volunteers in both first and second FIS applications (p<0.001). These results showed that FIS is validated in divergent direction. BDI score was higher in MS patients than healthy volunteers (p<0.001). There was no statistically significant difference between two study groups for cognitive subscale scores, after the effect of depression was eliminated (p>0.05). To assess the test-retest reliability, the scores of two FIS applications did not differ statistically (cognitive t=1.948 p>0.05, physical t=1.420 p=0.160, social t=1.470 p=0.146, total t=1.990 p=0.05). Intraclass correlation coefficients were 0.89 (99% confidence interval: 0.79-0.94) for cognitive, 0.95 (0.91-0.97) for physical, 0.91 (0.83-0.95) for social, and 0.93 (0.86-0.96) for total FIS scores (p<0.001). EDSS correlated with physical subscores in both applications of FIS.

Conclusion: Turkish version of FIS, which is valid and reliable, seems an appropriate tool for the assessment of the effects of fatigue in Turkish MS population.