Background of the FIB-4 Index in Japanese Non-Alcoholic Fatty Liver Disease

Objective We investigated the distribution and characteristics of the FIB-4 index of liver fibrosis in 1,441 Japanese men (age 50.7 +/- 10.2 years) and 304 women (age 53.9 +/- 10.3 years) who underwent comprehensive general health checkups and were identified as having non-alcoholic fatty liver disease. With respect to the FIB-4 index, differences according to sex, metabolic indices, and ultrasonic findings were investigated. Methods Among 9,255 individuals who underwent comprehensive general health checkups, 2,750 (29.8%) were found to have mild fatty liver or fatty liver based on ultrasound findings. After excluding patients who consumed >= 150 g alcohol/week (818 individuals), those testing positive for hepatitis B surface antigens or hepatitis C virus antibody (184 individuals), and those for whom data were insufficient (three individuals), we investigated the FIB-4 indices in the remaining 1,745 subjects. Results There were no sex differences in the FIB-4 index. A total of 1,370 patients (78.5%) exhibited a low cut-off index (COI) (<1.30), 357 (20.5%), exhibited an indeterminate COI (1.30-2.67), and 18 (1.0%) exhibited a high COI (>2.67). There were no associations between the FIB-4 index and the constituent factors of metabolic syndrome. In contrast, there was a significant difference in the ln FIB-4 index between the patients with and without mild fatty liver or fatty liver on ultrasound among men (0.006 +/- 0.43 and -0.092 +/- 0.39, p<0.001), but not women. Conclusion The FIB-4 index was is significantly lower in men, but not women, with fatty liver. The FIB-4 index must be calculated separately during medical checkups and evaluated in conjunction with ultrasound findings.