Validation of the Japanese version of the Modified Fatigue Impact Scale and assessment of the effect of pain on scale responses in patients with multiple sclerosis

Objective Fatigue is a major disabling symptom in multiple sclerosis (MS) patients. The Modified Fatigue Impact Scale (MFIS) is generally approved for evaluating fatigue in MS patients. However, a Japanese version of MFIS has not been established. The aims of the present study were to validate the Japanese MFIS and to investigate its relationship with pain in Japanese MS patients. Methods The MFIS was translated into Japanese by a professional translator. The Japanese version of MFIS was carried out for 30 relapsing–remitting MS patients during remission, and 30 age- and sex-matched healthy controls. MFIS for MS patients was repeated within 4 days to show the reliability. The Japanese version of the Multidimensional Fatigue Inventory and Pain Effects Scale were also carried out. Results No significant difference in MFIS score was found between the first and second assessments. Total scores were higher for the patients than for controls (P < 0.001); they correlated with those of the Kurtzke's Expanded Disability Status Scale (P < 0.001), Multidimensional Fatigue Inventory (P = 0.031) and Pain Effects Scale (P < 0.001). Positive correlations were found among subscales of the Japanese version of the MFIS in the patients. Conclusions A Japanese version of the MFIS validated fatigue evaluation in these patients.