Validation of the Japanese version of the Fisk Fatigue Severity Score (FFSS) in Japanese patients with primary biliary cirrhosis

Fatigue is considered to be a specific symptom of primary biliary cirrhosis (PBC), while the prevalence of fatigue in Japanese PBC patients remain unclear, probably due to lack of objective scales for assessment of fatigue in Japanese. In this study, we developed the Japanese version of Fisk Fatigue Severity Score (FFSS), frequently employed in the previous studies, and examined the validity and reliablity in 166 Japanese PBC patients. Cronbach's alfa coefficients in each subscale of the FFSS ranged from 0.94 to 0.96. The correlations between each subscale of FFSS and SF-36 were well acceptable. In particular, the 'vitality' and 'role physical' subscales of SF-36 were well correlated with subscales of FFSS. The factor analysis of the FFSS yielded 4 factors which explain 66% of the total variance. This study validated the Japanese version of FFSS, which provide a powerful tool for the evaluation of fatigue of Japanese PBC patients.