APRI Calculator

Estimate liver fibrosis from routine blood tests. Enter AST, its upper limit of normal, and your platelet count to compute the AST-to-Platelet Ratio Index (APRI).

Quick Facts

Formula
APRI = (AST ÷ AST ULN) × 100 ÷ platelets (×10⁹/L)
A non-invasive score for staging liver fibrosis from routine labs.
Cutoffs
0.5 / 1.5 for fibrosis; 1.0 / 2.0 for cirrhosis
Wai 2003 thresholds; APRI above 2.0 indicates cirrhosis (WHO).

Your Results

Calculated
APRI score
-
AST-to-Platelet Ratio Index
AST ratio
-
AST ÷ upper limit of normal
Significant fibrosis
-
METAVIR F2–F4 (cutoffs 0.5 / 1.5)
Cirrhosis
-
METAVIR F4 (cutoffs 1.0 / 2.0)

Ready

Enter AST, its upper limit of normal, and your platelet count, then press Calculate.

About the APRI

The AST to Platelet Ratio Index (APRI) is a non-invasive score that estimates the likelihood of liver fibrosis and cirrhosis from two routine blood values: aspartate aminotransferase (AST) and the platelet count. Wai and colleagues introduced it in 2003 as a low-cost alternative to liver biopsy in chronic hepatitis C, and the World Health Organization later adopted it for staging hepatitis B.

The formula

APRI divides the AST level by its laboratory upper limit of normal (ULN), multiplies by 100, then divides by the platelet count expressed in ×10⁹/L:

APRI = (AST ÷ AST ULN) × 100 ÷ platelet count

AST tends to rise and platelets tend to fall as scarring advances, so a higher APRI points toward more extensive fibrosis. The AST ULN is commonly 40 U/L but varies by laboratory, which is why this calculator asks you to enter the value shown on your own report.

Interpreting the score

  • Significant fibrosis (METAVIR F2 to F4): an APRI below 0.5 makes it unlikely, while an APRI above 1.5 makes it likely.
  • Cirrhosis (F4): an APRI below 1.0 makes it unlikely, while an APRI above 2.0 makes it likely. Values between the cutoffs are indeterminate.

When to consult a professional

APRI is a screening estimate, not a diagnosis. It can under- or over-estimate fibrosis, and an acute illness that raises AST or lowers platelets can distort the score. Always have a licensed healthcare provider interpret the result alongside your history, imaging, and other tests before making any treatment decision.

Frequently Asked Questions

What is a normal APRI score?
APRI is read against clinical cutoffs rather than a single normal value. An APRI at or below 0.5 makes significant liver fibrosis unlikely, and a value at or below 1.0 makes cirrhosis unlikely. Higher scores raise concern and usually prompt further testing such as elastography or imaging.
What AST upper limit of normal should I use?
Use the upper limit of normal printed on your own lab report, because reference ranges differ between laboratories. Many validation studies and the World Health Organization use 40 U/L. Entering a different ULN scales the APRI proportionally, so match it to the lab that measured your AST.
What APRI value suggests cirrhosis?
In the original validation by Wai and colleagues and in WHO guidance, an APRI above 2.0 is consistent with cirrhosis, while a value at or below 1.0 argues against it. Scores between 1.0 and 2.0 are indeterminate and need additional evaluation such as elastography or imaging.

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