Liver Fibrosis Staging & FIB-4 Terms Glossary

July 20, 2026

A FIB-4 result from the FIB-4 calculator often comes with follow-up terms from a report or a doctor’s note. Here’s what the most common ones mean.

Fibrosis Stages (F0-F4)

The standard histological scale for liver scarring severity, from a liver biopsy or estimated by non-invasive tests:

F0 — no fibrosis
F1 — mild, portal fibrosis without septa
F2 — moderate, a few septa
F3 — severe (bridging fibrosis) — this and F4 are what FIB-4 is specifically designed to flag (“advanced fibrosis”)
F4 — cirrhosis, the most advanced stage

FIB-4’s “high risk” category is aimed at identifying F3-F4 (advanced fibrosis), not earlier stages — a low FIB-4 doesn’t rule out mild F1-F2 fibrosis, only the advanced stages that carry the most clinical significance.

Cirrhosis

The clinical term for F4 fibrosis — extensive, often irreversible scarring that impairs normal liver function and carries risk of complications like portal hypertension and liver failure. This is the outcome FIB-4 screening aims to catch early enough to intervene before it develops.

Elastography (FibroScan / Transient Elastography)

A non-invasive imaging test that measures liver stiffness (a proxy for fibrosis) using ultrasound-based technology, without needing a biopsy. This is the typical next step after an indeterminate or high FIB-4 result on the FIB-4 calculator, per AASLD practice guidance.

Liver Biopsy

The historical gold-standard method for directly staging fibrosis by examining a tissue sample — invasive, with real procedural risk, which is exactly why FIB-4 and elastography exist as non-invasive alternatives to reduce how often biopsy is actually needed.

Negative Predictive Value (NPV) / Positive Predictive Value (PPV)

NPV measures how reliable a low (negative) score is at truly ruling out disease; PPV measures how reliable a high (positive) score is at truly confirming it. FIB-4 has strong NPV (over 90%) but weaker PPV (around 65% even at the stricter cutoff) — meaning it’s much better at telling you fibrosis is unlikely than at confirming it’s present. See the FIB-4 calculator for how this shapes the risk categories.

MASLD / MASH (Newer Terms Replacing NAFLD / NASH)

Metabolic dysfunction-associated steatotic liver disease (MASLD) and its more severe form, MASH, are the updated names for what was previously called non-alcoholic fatty liver disease (NAFLD) and NASH — a nomenclature change adopted by AASLD and other liver societies to better reflect the metabolic drivers of the disease. Older sources and some calculators, including references elsewhere on this site, may still use NAFLD/NASH — both refer to the same underlying condition.

Hepatology

The medical specialty focused on liver disease — the specialist referral point when FIB-4 and follow-up non-invasive testing suggest advanced fibrosis risk. See FIB-4 for primary care: when to refer to hepatology for the decision pathway.

Using This Glossary

Match these terms against a lab report or clinical note, then use the FIB-4 calculator to calculate or double-check the score itself. See understanding your liver panel for what AST, ALT, and platelet count mean individually.