APRI Score

AST to Platelet Ratio Index (APRI) for estimating liver fibrosis and cirrhosis.

Gastroenterology GastroenterologyEvidence-BasedUpdated 2026-07

Clinical Notes

Formula

[(AST / AST ULN) × 100] / Platelet Count

Clinical Notes

The APRI Score is a simple non-invasive marker for liver fibrosis using AST and platelet count.

References

Wai CT et al. Hepatology. 2003.
WHO Hepatitis Guidelines.
AASLD Practice Guidance.

Calculator Information

Specialty

Gastroenterology

📋 Reference Ranges

Reference ranges for this calculator
Classification	Range
Low Risk	<0.5
Intermediate Risk	0.5–1.5
Significant Fibrosis	>1.5
Suggestive of Cirrhosis	>2.0

What This Calculator Measures

Calculates the AST-to-Platelet Ratio Index (APRI) to estimate the likelihood of significant liver fibrosis and cirrhosis from AST and platelet count, particularly in chronic hepatitis.

How to Use

Enter the patient's AST, the AST upper limit of normal (ULN) for the laboratory, and the platelet count.
Confirm the correct local ULN, because the result scales directly with the ratio AST/ULN.
Interpret the score against the 0.5, 1.5, and 2.0 thresholds.

Interpretation Guide

APRI <0.5 indicates low likelihood of significant fibrosis; 0.5–1.5 intermediate probability; >1.5 significant fibrosis is likely; >2.0 is suggestive of cirrhosis.

Clinical Significance

APRI is a simple, laboratory-only index endorsed by WHO for fibrosis screening in chronic hepatitis, enabling risk stratification in settings without access to elastography.

When to Use

Non-invasive fibrosis estimation in chronic hepatitis, especially HCV
WHO-endorsed fibrosis screening in resource-limited settings
Risk stratification where elastography is unavailable

When Not to Use

Acute hepatitis with a transient AST flare
Thrombocytopenia due to non-portal-hypertension causes
Children and adolescents
When the laboratory AST ULN is uncertain

Limitations

The result depends on the chosen AST ULN, which varies between laboratories.
Accuracy is lowest in the intermediate band (0.5–1.5).
Platelet disorders unrelated to fibrosis confound the score.
The model is best validated in chronic hepatitis C.

Worked Example

A 48-year-old man with chronic hepatitis C has AST 120 U/L, an AST upper limit of normal of 40 U/L, and platelets 150 ×10⁹/L.

Inputs:

ast: 120

uln: 40

platelets: 150

APRI = ((120 / 40) × 100) / 150 = 2.0 — significant fibrosis is likely, bordering the cirrhosis threshold (>2.0).

Evidence

Source: Hepatology Literature
Reference: Wai CT, et al. A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C. Hepatology. 2003;38:518-526.
Reviewed By: MedCalcHub Clinical Team
Version: 1.0
Updated: 2026-08

Wai CT, et al. Hepatology. 2003;38:518-526.

References

Wai CT, et al. A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C. Hepatology. 2003;38:518-526. (Original model)

Disclaimer: This calculator is intended for educational and clinical decision support. APRI is a screening index; fibrosis stage should be confirmed with further testing when clinically indicated.