What is the FIB-4 score?
FIB-4 (fibrosis-4) is a simple, non-invasive index that estimates the stage of scarring (fibrosis) in the liver. It uses four values that are routinely available: the patient's age and three standard blood test results.
Unlike the other calculators on this site, FIB-4 does not give a risk over a period of years. It gives a single number, which is then read against two thresholds.
How is it calculated?
FIB-4 = (age in years × AST) / (platelet count × √ALT)
- AST - aspartate aminotransferase, in IU/L
- ALT - alanine aminotransferase, in IU/L
- Platelet count - in 109/L
How is the score read?
- Below 1.45 - low.
- 1.45 to 3.25 - indeterminate.
- Above 3.25 - high.
These are the thresholds from the paper that described the index. The score is shown to two decimal places because a value close to a threshold matters.
Who developed it?
FIB-4 was described by Sterling and colleagues in 2006, in patients with HIV and hepatitis C co-infection. The paper is listed on the publications page.
Which people can have a score calculated?
The calculator can be used for people aged between 18 and 99 years. It accepts AST and ALT values between 5 and 500 IU/L, and a platelet count between 10 and 600 × 109/L.
Who is responsible for this calculator?
FIB-4 is an aid to clinical judgement and not a diagnosis. All medical decisions need to be taken by a patient in consultation with their doctor.