Validity and reliability of Korean version of Modified Fatigue Impact Scale (MFIS) for Korean patients with multiple sclerosis

Background: To determine the validity and reliability of the Korean version of the Modified Fatigue Impact Scale (MFIS-K) questionnaire for patients with multiple sclerosis (MS). Methods: We prospectively enrolled 52 patients with MS and 102 healthy controls. Subjects were asked to complete the Korean version of Fatigue Severity Scale (FSS) and MFIS-K. To evaluate sleep quality, depression, pain, and quality of life, patients completed the Pittsburgh Sleep Quality Index (PSQI), the Beck Depression Scale II (BDI), the Brief Pain Inventory (BPI), and the Short Form 36 Health Survey (SF-36). Results: It was demonstrated that MFIS-K has appropriate construct validity with distinctive 3 factors (cognitive, physical, and psychosocial). The criterion validity was also confirmed with the total score and the factor scores of the patients with MS, which were all significantly higher than those of healthy controls. Convergent validity of the MFIS-K was verified with the correlations with Fatigue Severity Scale (FSS) and other concurrent measures of sleep disturbances, depression, pain, and limitations in activities due to health problems. Furthermore, the internal consistency, temporal stability, and score consistency of the MFIS-K turned out acceptable. Discussion: Our results indicate that the Korean version of MFIS is a valid and reliable scale to assess fatigue in the Korean MS population.