The FIB4 index was developed in 2006 by Sterling as a non-invasive method to diagnose liver fibrosis and combines aspartate aminotransferase (AST) levels, alanine aminotransferase (ALT) levels, platelet count, and age.
The index was originally used for staging liver fibrosis in HCV patients with HIV and, thereafter, has been used to quantify fibrosis of various liver diseases, including HCV (Hepatitis C virus) or HBV (Hepatitis B virus) infection, alcoholic liver disease, and non-alcoholic fatty liver disease. As the FIB4 index is calculated using only clinical laboratory test values and age, it is a completely objective evaluation, similar to the ALBI score. Moreover, the FIB4 index uses no numerical values directly correlated with liver synthetic ability or metabolic ability, such as albumin, total bilirubin, and prothrombin levels; therefore, not a single variable in this index overlaps with those in the ALBI and Child–Pugh scores. Another advantage of the FIB4 index is that it does not include the variables used in conventional integrated scores, which tend to vary with other factors.
Fibrosis-4 (FIB4) Scoring System for Liver Fibrosis
The FIB4 index is an indicator of hepatic fibrosis calculated on the basis of age, aspartate aminotransferase (AST) levels, alanine aminotransferase (ALT) levels, and platelet count, but it does not include variables directly related to liver function.
FIB4 = Age x AST / (Platelet x sqr(ALT))
Age in years old, AST in U/L (Norm: 15 – 41), Platelet count in 10³/µL (Norm: 150 – 350 × 10³/µL), ALT in Norm: 1 – 35 U/L (Norm: 1 – 35 U/L).
The diagnostic cut-off values of the FIB 4 index produce a negative predictive value of 94.7% with a sensitivity of 73.4%, and a positive predictive value of 82.1% with a specificity of 98.2%.
Interpretation of FIB-4
Points < 1.45: Cirrhosis less likely
Points ≥ 1.45 and ≤ 3.25: Indeterminate
Points > 3.25: Cirrhosis most likely
Abbreviations: sqr, square root
- Kariyama K, Nouso K, Toyoda H, Tada T, Hiraoka A, Tsuji K, Itobayashi E, Ishikawa T, Wakuta A, Oonishi A, Kumada T, Kudo M, Group OBOTRPEFHRS, Group H. Utility of FIB4-T as a Prognostic Factor for Hepatocellular Carcinoma. Cancers (Basel). 2019 Feb 10;11(2):203. [Medline]
- Salomone F, Micek A, Godos J. Simple Scores of Fibrosis and Mortality in Patients with NAFLD: A Systematic Review with Meta-Analysis. J Clin Med. 2018 Aug 15;7(8):219. [Medline]
Created Mar 18, 2021.