FIB-4 Index (Fibrosis-4)

Non-invasive scoring system to estimate liver fibrosis using age, AST, ALT, and platelet count.

Age

years

Patient age in years

AST

U/L

Aspartate aminotransferase

ALT

U/L

Alanine aminotransferase

Platelet Count

10^9/L

Platelet count (x10^9/L)

References

FIB-4, APRI, and AST/ALT ratio compared to FibroScan for hepatic fibrosis in NAFLD - BMC Gastroenterology / NIH PMC
Fibrosis scoring systems (FIB-4 and ELF) - British Liver Trust

Clinical Notes & Warnings

Most reliable for ages 35-65 years.
Developed for chronic hepatitis C; validated for NAFLD/NASH.
Not validated for acute hepatitis or children.
May overestimate fibrosis in patients >65 years.

Cutoffs: <1.30 = low risk, 1.30-2.67 = indeterminate, >2.67 = high risk of advanced fibrosis. Alternative UK pathway: 0-2 mild, 3-4 moderate, 5-6 severe.