Fibrosis-3 Index: A New Score to Predict Liver Fibrosis in Patients With Nonalcoholic Fatty Liver Disease Without Age as a Factor

Background and aims: The Fibrosis-4 (FIB-4) index has been used to predict liver fibrosis in various liver diseases, including nonalcoholic fatty liver disease (NAFLD). Because the FIB-4 formula uses age, different cutoff values may be required for different age groups, making the interpretation difficult. To avoid the influence of age, we attempted to create a new score, the Fibrosis-3 (FIB-3) index.

Methods: The FIB-3 index was created using a training cohort of 735 NAFLD cases using aspartate aminotransferase, alanine amino transferase, and platelet for predicting fibrosis. The abilities of the FIB-3 and FIB-4 indices were compared among different age groups in the training cohort and validation cohort with 324 patients. The FIB-3 index was also compared with other liver fibrosis indices.

Results: The area under the receiver operating characteristic curve (AUROC) values of the FIB-3 and FIB-4 indices for predicting F3-F4 fibrosis were 0.764 and 0.762, respectively, in the training cohort. No difference in the AUROC values was observed between the 2 indices in the validation cohort. The differences in the accuracies of FIB-3 between elderly and nonelderly patients were 0.140 and 0.178, respectively, in each cohort and were smaller than those of FIB-4 index (0.199 and 0.336, respectively). Analysis using a joined cohort revealed that the AUROC of FIB-3 for predicting F3-F4 fibrosis (0.774) was the highest among the 5 fibrosis scores examined and was comparable to that of FIB-4.

Conclusion: The FIB-3 index is an improved version of the FIB-4 index and can effectively predict liver fibrosis in patients with NAFLD.