Validation study of age‐independent fibrosis score (Fibrosis‐3 index) in patients with metabolic dysfunction‐associated steatotic liver disease

Abstract Background and Aims Because the accuracy of the Fibrosis‐4 (FIB‐4) index for predicting liver fibrosis changes with age, the need for different cut‐offs in various age groups has frequently been discussed. We developed the age‐independent score, the Fibrosis‐3 (FIB‐3) index, and have shown its usefulness in patients with metabolic dysfunction‐associated steatotic liver disease (MASLD). This study aimed to validate the diagnostic ability of the FIB‐3 index to predict fibrosis progression using a large new patient cohort. Methods The ability of the FIB‐3 index to predict liver fibrosis was analyzed by comparing it with that of the FIB‐4 index using data from 1398 patients with MASLD enrolled in the Asia‐based clinical outcome NAFLD study. Results The areas under the receiver operating characteristic curves for predicting fibrosis stage F3 or higher were not different between the FIB‐3 and FIB‐4 indices in the entire cohort. Using the single ideal cut‐offs of the indices (3.41 for FIB‐3 index and 2.01 for FIB‐4 index), the predictive accuracy of the FIB‐3 index was not significantly different from that of the FIB‐4 index among patients aged <60 years; however, the accuracy of the FIB‐3 index was significantly higher than that of the FIB‐4 index in those aged ≥60 years (0.645 and 0.529, respectively; p < 0.0001). Conclusion The high ability of the FIB‐3 index with a single cut‐off to predict liver fibrosis in patients with MASLD was confirmed. The FIB‐3 index could serve as a useful tool for assessing liver fibrosis regardless of age.