What APRI score indicates significant fibrosis?

An APRI score above 1.5 is the validated cutoff to rule in significant fibrosis (Metavir ≥F2) in chronic hepatitis C, while an APRI below 0.5 rules it out with high negative predictive value. For cirrhosis (F4), an APRI above 2.0 rules in cirrhosis, whereas a score of 1.0 or lower rules it out.

What is the AST upper limit of normal (ULN)?

The ULN is the highest AST value considered normal by your specific laboratory. It varies by lab and patient sex — a common default is 40 U/L for adults, but your lab report or reference range should confirm this. Using the correct ULN is important for an accurate APRI calculation.

Is APRI valid for conditions other than hepatitis C?

APRI was originally validated in chronic hepatitis C. It has been studied in hepatitis B, NAFLD, and HIV/HCV co-infection, but its accuracy is lower in these populations. For NAFLD, FIB-4 index is often preferred. Always interpret APRI in the context of the specific clinical diagnosis.

Can APRI replace liver biopsy?

APRI is a non-invasive alternative, not a replacement. It is useful for ruling out significant fibrosis (low APRI) or suggesting cirrhosis (high APRI), but scores in the intermediate range (0.5–1.5) often remain indeterminate and may still require biopsy for definitive staging.

Why does platelet count affect the fibrosis score?

In liver fibrosis and cirrhosis, portal hypertension leads to splenomegaly, which sequesters platelets and reduces circulating platelet count. Elevated AST reflects hepatocyte injury. The combination of high AST and low platelets — captured by the APRI formula — correlates with advancing fibrosis.

APRI Score Calculator (Liver Fibrosis)

Enter AST, its upper limit of normal, and platelet count to compute APRI and get a fibrosis/cirrhosis risk interpretation.

Lab Values

AST (U/L)

Aspartate aminotransferase from serum chemistry panel

AST Upper Limit of Normal — ULN (U/L)

Lab-specific reference ceiling; commonly 40 U/L for adults

Platelet Count (10⁹/L)

Enter in 10⁹/L — e.g. type 120 for 120,000/µL

APRI Score & Interpretation

Enter lab values and click Calculate to see the APRI score.

Threshold Reference

< 0.5 — Significant fibrosis unlikely (rules out ≥F2)

0.5 – 1.5 — Indeterminate range; ≤ 1.0 rules out cirrhosis

1.5 – 2.0 — Significant fibrosis likely (≥F2); cirrhosis indeterminate

> 2.0 — Cirrhosis likely (rules in F4); specialist evaluation indicated

For clinical decision support only. Not a substitute for clinical judgment or liver biopsy.

Summary

The APRI (AST-to-Platelet Ratio Index) is a non-invasive blood test score used to estimate the likelihood of significant liver fibrosis or cirrhosis, primarily validated in chronic hepatitis C. It requires only two routine lab values — serum AST and platelet count — and applies the formula: APRI = (AST ÷ ULN_AST) ÷ Platelet count (10⁹/L) × 100. An APRI below 0.5 rules out significant fibrosis, above 1.5 indicates significant fibrosis (≥F2), and above 2.0 suggests cirrhosis (scores ≤1.0 rule out cirrhosis), though cutoffs should be interpreted alongside clinical findings and elastography.

How it works

Enter the serum AST value in U/L from the patient's lab report.
Confirm the AST upper limit of normal (ULN) for your laboratory — commonly 40 U/L.
Enter the platelet count in 10⁹/L (e.g., type 150 for 150 × 10⁹/L).
The tool computes: APRI = (AST / ULN_AST) / Platelet × 100.
Review the result: APRI < 0.5 makes significant fibrosis unlikely; 0.5–1.5 is indeterminate; > 1.5 suggests significant fibrosis (≥F2); > 2.0 suggests cirrhosis.

Use cases

Initial screening for significant fibrosis in chronic hepatitis C patients before biopsy.
Monitoring disease progression over serial blood draws without repeat imaging.
Guiding decisions on liver biopsy necessity in resource-limited settings.
Assessing cirrhosis risk alongside FIB-4 index for a non-invasive fibrosis panel.
Teaching clinical scoring systems in hepatology and internal medicine education.
Pre-treatment assessment before initiating antiviral therapy for hepatitis C.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu