APRI Calculator (AST to Platelet Ratio)
The APRI Calculator (AST to Platelet Ratio Index) is a non-invasive screening score for liver fibrosis and cirrhosis. It compares AST against its upper limit of normal relative to the platelet count. The formula used is: APRI = (AST ÷ AST upper limit) ÷ platelet count × 100.
Rates and fees change frequently. Always confirm the current figures
with the official authority before relying on this result.
- Screening estimate for fibrosis. Requires physician interpretation.
Formula
APRI = (AST ÷ AST upper limit) ÷ platelet count × 100
- The APRI Calculator updates instantly as you change AST, its upper limit, or the platelet count.
- Formula: APRI = (AST ÷ AST upper limit) ÷ platelet count × 100
- Input definitions: • AST: aspartate aminotransferase in U/L • AST upper limit of normal: your lab's upper reference limit for AST in U/L • Platelet count: in ×10⁹/L
- APRI under 0.5 makes significant fibrosis unlikely; above 1.5 suggests significant fibrosis; above 2.0 suggests cirrhosis.
- Use your own laboratory's AST upper limit of normal for the most accurate result.
- This is a screening estimate and does not replace formal staging such as elastography or biopsy.
Example Calculation
Inputs
- AST: 60 U/L
- AST upper limit of normal: 40 U/L
- Platelet count: 200 ×10⁹/L
For AST 60 U/L with an upper limit of 40 U/L and platelets of 200 ×10⁹/L: APRI = (60 ÷ 40) ÷ 200 × 100 = 0.75, which is indeterminate.
Frequently asked questions
What is APRI used for?
It is a simple, non-invasive index that estimates the likelihood of significant liver fibrosis or cirrhosis, often in chronic hepatitis C or B.
How is APRI calculated?
APRI = (AST ÷ AST upper limit of normal) ÷ platelet count × 100, using platelets in ×10⁹/L.
What do the results mean?
Under 0.5 makes significant fibrosis unlikely, 0.5 to 1.5 is indeterminate, above 1.5 suggests significant fibrosis, and above 2.0 suggests cirrhosis.
Which AST upper limit should I use?
Use the upper limit of normal from the lab that ran the test, since reference ranges vary between laboratories.
Can APRI replace a biopsy?
No. It is a screening estimate. Definitive staging may need elastography or liver biopsy, interpreted by a clinician.
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