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In the study in which the FIB-4 index was developed, examining a small piece of liver tissue could be skipped for 71% of the group in which the score was tested. These were people with two long-term viral conditions, one of which affects the liver.[1]
On this page you can read what the FIB-4 index is, what the guidelines say about a value that is too low or too high, what affects your value and which values are best to look at alongside it.
Also known as: FIB-4 score, Fibrosis-4 score. At the lab: n/a.
The FIB-4 index is a calculated score that estimates how much scar tissue there may be in your liver. It is not a separate measurement in your blood. The score is calculated from ordinary blood values that are often already measured.[1]
The calculation uses your age, your AST, your ALT and the number of platelets in your blood. A higher age and a higher AST make the score higher. More platelets and a higher ALT make the score lower.[1]
A low score can indicate that there is little scar tissue in the liver. A high score can point to more scar tissue. The index was designed as a simple test without a procedure. This way, the score can reduce the need to examine a small piece of liver tissue.[1]
Examining a small piece of liver tissue used to be the gold standard for determining how severe a liver condition is. Such a procedure carries risks. That is why tests without a procedure are being used more and more.[1]
Many other scores use tests that are not available everywhere. The researchers wanted a score that uses only routine blood values.[1]
In the study, the two cut-offs together correctly classified 87% of the 198 people with a score below 1.45 or above 3.25.[1]
| Score | What it can indicate | Who it is for |
|---|---|---|
| Below 1.45[1] | Can indicate that there is no advanced scar tissue. Of the people with this score, 90% had no advanced scar tissue. | People with two long-term viral conditions, one of which affects the liver |
| Between 1.45 and 3.25[1] | Falls between the two cut-offs. The study did not place these scores in a group. | People with two long-term viral conditions, one of which affects the liver |
| Above 3.25[1] | Can point to advanced scar tissue. Of the people with this score, 65% had advanced scar tissue. | People with two long-term viral conditions, one of which affects the liver |
Source: Sterling and colleagues, Hepatology 2006. A study of 832 people with two long-term viral conditions, one of which affects the liver.[1]
A score above 3.25 can point to advanced scar tissue in the liver. In the study, 97% of the people without advanced scar tissue stayed below that cut-off.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
In the formula, your age in years is multiplied by your AST. So if your other values stay the same, the score rises as the years go by.[1]
AST sits above the line of the fraction in the formula. This means every rise in your AST feeds straight into the score.[1]
Your platelet count sits below the line of the fraction. Fewer platelets make the score higher. In the study, the platelet count was clearly linked to scar tissue in the liver.[1]
Your ALT counts through its square root, below the line of the fraction. This means a change in your ALT has a weaker effect than the same change in your AST.[1]
The FIB-4 index is included in BioProfile 77, 87, 121 and 150.[2]
The BioProfile editorial team wrote this page on 16 October 2026 from the sources below, which we read on 16 October 2026. Every number on this page comes from one of those sources, with that source's number beside it. An expert has yet to review this page; once the review is done, the expert's name and the date of the review will appear at the top. This page explains and does not diagnose. Discuss an abnormal value with your GP.
