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APRI (AST-to-platelet ratio index)

A simple index relating AST as a multiple of its upper limit to platelets, to estimate significant fibrosis and cirrhosis, particularly in chronic hepatitis C.

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Check the population, units and version. The result shows the formula or classification; it does not make an automatic treatment decision.

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Method · Limits of application

APRI/Wai 2003: 100×(AST/ULN)/platelets 10^9/L

Wai’s 2003 APRI was developed in treatment-naive patients with chronic hepatitis C who underwent liver biopsy, with separate training and validation cohorts. Significant fibrosis in the study corresponded to Ishak ≥3. Application to other liver diseases or populations and the cutoffs of the version used require specific evidence; the calculation alone does not establish a histological diagnosis.

Conditions of use

Check the population, units, inclusion and exclusion criteria, and version in the original source. A result alone does not establish a diagnosis, discharge decision or prescription.

Documented parameters

Aspartate aminotransferase (AST) · U/L
Laboratory upper limit of normal for AST · U/L
Platelets · × 10³/mm³

4/4 reference cases checked. Numerical tests are not clinical validation.

Sources and documentation

Documented formula

Transcribed from the source or a recorded revision; this is not a clinical recommendation.

APRI = (AST ÷ upper limit of normal) ÷ platelets (10⁹/L) × 100.

References

Wai CT et al. A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C. Hepatology, 2003.

Identifier: apri

Original clinical content: Brazilian Portuguese.

Method version

APRI/Wai 2003: 100×(AST/ULN)/platelets 10^9/L

apri@native-2026-10-03+3d4ec823fbd3

Source for the active edition

The bibliographic edition identifies the source. By itself, it proves neither full conformity of the formula nor clinical approval.

Synthetic cases checked (4)

Synthetic cases for checking the implementation, with no patient data.

Case 1

reference-001

Inputs

Aspartate aminotransferase (AST): 30 U/L
Laboratory upper limit of normal for AST: 40 U/L
Platelets: 250 × 10³/mm³

{
  "ast": 30,
  "lsn": 40,
  "plq": 250
}

Expected result

{
  "apri": 0.3
}

Actual result

{
  "apri": 0.3
}

Case 2

reference-002

Inputs

Aspartate aminotransferase (AST): 60 U/L
Laboratory upper limit of normal for AST: 40 U/L
Platelets: 150 × 10³/mm³

{
  "ast": 60,
  "lsn": 40,
  "plq": 150
}

Expected result

{
  "apri": 1
}

Actual result

{
  "apri": 1
}

Case 3

reference-003

Inputs

Aspartate aminotransferase (AST): 80 U/L
Laboratory upper limit of normal for AST: 40 U/L
Platelets: 100 × 10³/mm³

{
  "ast": 80,
  "lsn": 40,
  "plq": 100
}

Expected result

{
  "apri": 2
}

Actual result

{
  "apri": 2
}

Case 4

reference-004

Inputs

Aspartate aminotransferase (AST): 120 U/L
Laboratory upper limit of normal for AST: 40 U/L
Platelets: 100 × 10³/mm³

{
  "ast": 120,
  "lsn": 40,
  "plq": 100
}

Expected result

{
  "apri": 3
}

Actual result

{
  "apri": 3
}

Code and reproducibility

This tool’s code on GitHub

Download code and tests

Sources, version and reproduction instructions

The code tests are technical checks. Clinical approval and professional translation review are recorded separately.

Relationship with cancer research

General context — relationship to be defined

A resource for general clinical contexts. This edition does not assign a specific oncological relationship; selecting it for a study requires a justified question, population and purpose.