FibroTest, sold in the United States under the name FibroSure, estimates how much scarring has built up in your liver from five proteins measured in a single blood sample, read together with your age and sex. It is a laboratory test, not a home measurement, and not all five proteins sit on a standard liver panel: you must ask for them by name, or order the packaged version from a laboratory that offers it.
It was developed in the early 2000s to stage fibrosis in chronic hepatitis C without a needle biopsy, and has since been studied in hepatitis B and in fatty liver disease.
What you need
One venous blood draw, with each result in the units your laboratory prints:
- Alpha-2-macroglobulin — a protease inhibitor made by the liver.
- Haptoglobin — the protein that binds free hemoglobin.
- Apolipoprotein A1 — the main protein of HDL particles.
- Total bilirubin — from any routine liver panel.
- GGT, gamma-glutamyl transferase — also routine.
- Your age and sex.
Bilirubin and GGT are ordinary requests; the first three usually are not, and are often sold only inside the branded panel — a paid test, not part of a routine check-up. If all five are hard to arrange, the FIB-4 Fibrosis Index asks a narrower version of the same question from values most people already have: age, ALT, AST and platelet count.
How the measurement works
Each marker tracks a different consequence of a scarring liver. Alpha-2-macroglobulin rises as fibrosis advances, because the cells that build scar also slow its breakdown. Haptoglobin and apolipoprotein A1 fall, since both are made by liver cells and synthesis suffers as working tissue is replaced — the same reason Albumin drops in advanced disease. Bilirubin rises when clearance begins to fail, and GGT with ongoing injury or obstructed bile flow. Age and sex enter because several of these values drift with both.
The five are combined with fixed weights into a single figure. Those weights are proprietary — they belong to the company that patented the test and are not printed on a lab report — so there is no formula to check by hand and no way to eyeball a stage from raw values. Entering the five results with your age and sex into FibroTest returns the score and the stage it corresponds to on the METAVIR, Knodell and Ishak systems.
How to read the result
The score runs from 0 to 1 and behaves like a probability of significant scarring rather than a direct measurement of it. Score is converted to stage by the test’s own published table, and neighboring stages sit in narrow slices of the range, so read the stage the calculator prints, not the decimal. The panel is strongest at the two ends of the scale and weakest at telling one intermediate stage from the next.
| Where the score sits | What it suggests | What usually follows |
|---|---|---|
| Low end | No fibrosis, or minimal fibrosis only | Advanced scarring unlikely; attention shifts to the cause |
| Middle | Intermediate, and the least reliable part of the scale | Elastography or a second, different test |
| Upper end | Advanced fibrosis or cirrhosis | Specialist assessment and surveillance |
What it does not tell you
It does not see your liver. A biopsy shows architecture, inflammation and fat; this panel infers one of those from blood proteins. It says nothing about how much fat is present, and inflammatory activity needs a companion calculation built on ALT.
Several ordinary conditions push it the wrong way. Anything that breaks down red blood cells consumes Haptoglobin and can lift the score in a healthy liver; so can Gilbert syndrome, a harmless inherited variant that raises bilirubin. Acute infection raises haptoglobin instead and can mask real fibrosis, and obstructed bile ducts or drugs that alter apolipoprotein A1 distort it too. Mention recent illness, alcohol and every medication to whoever interprets the result.
It was validated mostly in people already known to have chronic liver disease, hepatitis C above all. In an unselected population, where advanced fibrosis is rare, a high score is likelier to be a false alarm. And it names neither cause nor trajectory: it cannot say whether alcohol, a virus or Steatohepatosis did the damage, or what would change it.
Related reading
- Which Blood Tests Reflect Aging and How to Read Them
- How to Improve Metabolic Health: A Practical Guide
- Laboratory tests
- Alkaline phosphatase (ALP)
Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.