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APRI Liver Score Calculator

Screen for significant liver fibrosis and cirrhosis from AST, its upper limit of normal and platelet count.

How it is calculated

APRI compares how far AST sits above its normal ceiling with the platelet count: APRI = (AST ÷ AST upper limit of normal) ÷ platelets × 100. AST and its upper limit are in U/L, platelets in ×109/L. If you leave the upper limit empty, the engine assumes 40 U/L; use your lab's own figure when it differs. The tool also shows AST as a multiple of the upper limit. Bands used: below 0.5 fibrosis unlikely, 0.5 to under 1.0 indeterminate, 1.0 to under 1.5 cirrhosis possible, 1.5 to under 2.0 significant fibrosis likely, 2.0 and above cirrhosis likely. Zero or negative inputs return no result, and so does a platelet count above 5,000, which is taken as a unit slip (cells per µL instead of ×109/L). Cut-offs differ between guidelines and diseases.

Worked example

AST is 80 U/L, the lab's upper limit is 40 U/L and platelets are 150 ×109/L. AST is 80 ÷ 40 = 2.00 times the upper limit, which the tool prints as 2.00 x upper limit of normal. Dividing by platelets gives 2 ÷ 150 = 0.01333, and multiplying by 100 gives an APRI of 1.33. That falls in the 1.0 to 1.5 band, so the tool says cirrhosis is possible (WHO cutoff for cirrhosis is 1.0 in hepatitis C). The AST alone is only twice normal; the low-normal platelet count is what lifts the score.

Try this example →

Common mistakes

  • Typing platelets per µL (150,000) instead of ×109/L (150). The tool treats anything above 5,000 as this slip and shows no result, so convert before entering.
  • Leaving the upper limit empty when your lab uses a different one (for example 33 or 50 U/L); the tool silently falls back to 40.
  • Entering the AST ratio (2.0) in the AST field instead of the measured value in U/L.
  • Forgetting the final ×100: APRI of 0.013 is not the same as 1.33, and the bands only work on the multiplied value.
  • Applying the result to a different condition than the one the cut-offs were built for; the tool's own interpretation mentions hepatitis C for the 1.0 cirrhosis cut-off.

About this calculator

The AST-to-Platelet Ratio Index (APRI) is a non-invasive screening score for liver fibrosis and cirrhosis, calculated as APRI = [(AST ÷ AST upper limit of normal) ÷ platelet count (10⁹/L)] × 100. It works because liver fibrosis both raises AST (from ongoing liver cell damage) and lowers platelet count (from portal hypertension and reduced thrombopoietin production as liver function declines), so the ratio of the two tracks disease severity.

Hepatologists use APRI, originally validated in hepatitis C patients, as a first-line screening tool before resorting to liver biopsy or elastography — a score below 0.5 makes significant fibrosis unlikely, a score from 1.0 to 1.5 makes cirrhosis possible, 1.5 to 2.0 makes significant fibrosis likely, and a score above 2.0 makes cirrhosis likely, with values from 0.5 to 1.0 indeterminate and requiring further testing. Because it only needs two common lab values, it's widely used in resource-limited settings where imaging or biopsy access is restricted.

This calculator takes your AST, its upper limit of normal, and platelet count and returns the APRI score with an interpretation.

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