FIB-4 Index

Sterling RK, Lissen E, Clumeck N, et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. FIB-4 = (age·AST)/(platelets·√ALT); < 1.45 had a 90% negative predictive value for advanced fibrosis and > 3.25 a 65% positive predictive value, avoiding biopsy in ~70% of patients.

FIB-4 has since been validated in chronic hepatitis C, hepatitis B, and non-alcoholic fatty liver disease; in adults over ~65 the lower cut-off is commonly raised to 2.0 to preserve specificity.

The 2023 AASLD NAFLD/MASLD guidance and the EASL–EASD–EASO guideline recommend FIB-4 as the first-line non-invasive test to risk-stratify for advanced fibrosis in primary and specialist care.