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Hepatology

AST to Platelet Ratio Index (APRI)

APRI is a simple, non-invasive score to estimate hepatic fibrosis severity in chronic hepatitis C and other liver diseases. Enter AST and platelet count to calculate the index.

Use lab-specific upper limit, typically 35–40 IU/L.

Inputs

  • AST: 80
  • ULN AST: 35
  • Platelets: 150

APRI score

1.52

Typical range 0–2

High likelihood of significant fibrosis

APRI ≥ 1.0 suggests advanced fibrosis or cirrhosis. Confirm with elastography, imaging, or liver biopsy when appropriate.

Consider combining with FIB-4, ultrasound elastography, or FibroScan® to refine staging.

How to Use This Calculator

1

Obtain recent lab values

Use the same-day serum AST and platelet count. Confirm your laboratory’s AST upper limit of normal.

2

Enter the values and review the APRI score

The calculator outputs the APRI index and highlights the risk category for significant fibrosis.

3

Plan next steps

High scores warrant further evaluation (elastography, biopsy) and prompt antiviral or antifibrotic therapy when indicated.

Formula

APRI = (AST / AST upper limit of normal) × 100 ÷ Platelet count (×10⁹/L)

  • AST and platelets should be from the same blood draw.
  • AST ULN depends on laboratory (commonly 35 IU/L for women, 40 IU/L for men).
  • APRI < 0.5 strongly suggests absence of significant fibrosis; APRI ≥ 1.5 has high specificity for cirrhosis.

Full Description

The AST to Platelet Ratio Index (APRI) is a validated non-invasive marker for staging liver fibrosis in chronic hepatitis C and other hepatopathies. Higher AST reflects hepatocellular injury, while thrombocytopenia correlates with portal hypertension and advanced fibrosis.

APRI is inexpensive and widely available, making it useful in resource-limited settings. However, it is influenced by hemolysis, acute inflammation, alcohol use, and medications. Integrate APRI with clinical assessment, imaging, and alternative fibrosis scores for comprehensive management.

Frequently Asked Questions

Can APRI be used in hepatitis B or NAFLD?

Yes, but performance varies. Combine with FIB-4 or transient elastography for better accuracy in non-HCV etiologies.

How often should APRI be repeated?

Repeat every 6–12 months in chronic hepatitis patients, or sooner if liver enzymes change significantly.

What if platelet count is very low due to another cause?

APRI may overestimate fibrosis in thrombocytopenia unrelated to portal hypertension. Interpret cautiously with hematology input.

Does AST have to be fasting?

Fasting is not required, but avoid timing after intense exercise or alcohol ingestion, which can elevate AST.