A liver fibrosis estimate from routine blood tests
Chronic liver diseases, such as hepatitis B or C, fatty liver disease or long-term heavy drinking, slowly replace healthy liver tissue with scar tissue. This fibrosis can progress silently over decades to cirrhosis, which raises the risk of liver failure and liver cancer. Measuring fibrosis used to require a liver biopsy. In 2003, Chun-Tao Wai and colleagues at the University of Michigan proposed a simple alternative based on two tests almost every patient already has.
The formula
APRI = (AST ÷ upper limit of normal for AST) ÷ platelet count (×10³/µL) × 100
- AST is a liver enzyme that rises as the liver is damaged.
- Platelets fall as fibrosis advances, because scarring raises pressure in the portal vein, enlarges the spleen and traps platelets there.
Interpreting the score
| APRI | Interpretation |
|---|---|
| 0.5 or less | Significant fibrosis unlikely |
| 0.5 to 1.5 | Indeterminate |
| Above 1.5 | Significant fibrosis likely |
| Above 2 | Cirrhosis likely |
Worked example
A patient has an AST of 80 U/L, with a laboratory upper limit of 40 U/L, and a platelet count of 150 ×10³/µL.
APRI = (80 ÷ 40) ÷ 150 × 100 = 1.33
The score falls in the indeterminate zone. Another test, such as FIB-4 or elastography, would be needed to classify the fibrosis.
Strengths and limits
- Cheap and available everywhere, which is why the World Health Organization’s hepatitis guidelines recommend it for settings without elastography.
- Many patients fall in the middle zone, where it cannot decide.
- AST rises for other reasons, such as recent alcohol intake, muscle injury or acute hepatitis, which inflate the score.
- Platelets fall for other reasons, such as some medications or bone marrow disorders.
- It was developed in hepatitis C. It performs less well in fatty liver disease, where FIB-4 or the NAFLD fibrosis score are preferred.
Your hepatologist or primary care doctor interprets the score together with imaging and the rest of your results.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.