The novel cutoff points for the FIB4 index categorized by age increase the diagnostic accuracy in NAFLD: a multi-center study

Background The FIB4 index is clinically useful, but because its formula includes age, the appropriate cutoff point may differ by age group. Here, new FIB4 index cutoff points were validated using cohort data from 14 hepatology centers in Japan. Methods The FIB4 index was determined in biopsy-confirmed NAFLD patients ( n = 1050) who were divided into four groups: ≤ 49, 50–59, 60–69, and ≥ 70 years. ROC analysis predicted advanced fibrosis in each age group; low and high cutoff points were defined by a sensitivity and specificity of 90%. The new and conventional cutoffs were compared for detecting advanced fibrosis. Results The modified low and high cutoff points were 1.05 and 1.21 in ≤ 49 years, 1.24 and 1.96 in 50–59 years, 1.88 and 3.24 in 60–69 years, and 1.95 and 4.56 in ≥ 70 years. In ≥ 60 years, the false-negative rate was increased using the modified high cutoff point, and the high cutoff point was better with the conventional cutoff point. The new proposed low and high cutoff points are 1.05 and 1.21 in ≤ 49 years, 1.24 and 1.96 in 50–59 years, 1.88 and 2.67 in 60–69 years, and 1.95 and 2.67 in ≥ 70 years; these cutoff points improved the accuracy of advanced fibrosis diagnosis. Conclusions FIB4 index cutoff points for predicting advanced fibrosis in NAFLD increased with age. Cutoff points modified by age improved the diagnostic accuracy of estimations of advanced liver fibrosis using the FIB4 index.