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APRI (AST to platelet ratio index)

Non-invasive estimate of liver fibrosis and cirrhosis (Wai 2003)

Sources last checked: 2026-10-27

APRI (AST to platelet ratio index)

Non-invasive estimate of liver fibrosis and cirrhosis (Wai 2003)

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Derived in 270 patients with chronic hepatitis C; accuracy is lower in other liver diseases, and about half of patients fall between the cut-offs. Acute hepatitis, haemolysis, muscle injury and causes of thrombocytopenia other than portal hypertension distort it.

Source: Wai CT, Greenson JK, Fontana RJ et al. A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C. Hepatology 2003;38(2):518-526.Open

Interpretation

≤ 0.5 — significant fibrosis unlikelyWai 2003: at or below the lower cut-off for significant fibrosis (0.5), and below the cirrhosis rule-out cut-off (1.0).
> 0.5–1.0 — indeterminate for fibrosisBetween Wai's two cut-offs for significant fibrosis; still at or below the cirrhosis rule-out cut-off (1.0).
> 1.0–1.5 — indeterminateIndeterminate for both significant fibrosis (0.5–1.5) and cirrhosis (1.0–2.0) in Wai 2003.
> 1.5–2.0 — significant fibrosis likelyAbove Wai's rule-in cut-off for significant fibrosis (> 1.5); indeterminate for cirrhosis.
> 2.0 — cirrhosis likelyAbove Wai's rule-in cut-off for cirrhosis (> 2.0).

What is the APRI (AST to platelet ratio index)?

The AST to platelet ratio index (APRI) combines two routine blood tests to estimate liver fibrosis. Wai and colleagues derived it in 2003 at the University of Michigan in 270 patients with chronic hepatitis C who had a liver biopsy, defining one pair of cut-offs for significant fibrosis (0.5 and 1.5) and one for cirrhosis (1.0 and 2.0).

When to use it

  • Initial non-invasive fibrosis assessment in chronic hepatitis C or B
  • Settings where elastography is not available
  • Combining with FIB-4 or elastography in a stepwise work-up

When not to use it

  • Acute hepatitis or a recent AST flare, which raises APRI without fibrosis
  • Thrombocytopenia from causes other than liver disease (e.g. ITP, chemotherapy, hypersplenism of other origin)
  • As the only test for staging fibrosis in MASLD — EASL favours FIB-4 followed by elastography

How it is calculated

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

Clinical pearls and limitations

  • Derived in 270 patients with chronic hepatitis C; accuracy is lower in other liver diseases, and about half of patients fall between the cut-offs. Acute hepatitis, haemolysis, muscle injury and causes of thrombocytopenia other than portal hypertension distort it.
  • The AST upper limit of normal from the reporting laboratory is part of the formula — using a different reference limit changes the result.
  • About half of patients fall between the cut-offs and need another test.
  • EASL 2021 considers APRI less accurate than FIB-4 and elastography for ruling cirrhosis in or out.
  • Haemolysis and muscle injury raise AST and therefore APRI.

Frequently asked questions

What APRI indicates cirrhosis?

In Wai 2003, APRI > 2.0 ruled cirrhosis in and ≤ 1.0 made it unlikely; values in between are indeterminate.

APRI or FIB-4?

FIB-4 adds age and ALT and generally performs better; both are first-line serum tests, and EASL recommends FIB-4 as the entry point in MASLD.

What upper limit of normal should I use for AST?

The upper reference limit printed by your laboratory, usually between 35 and 50 U/L.

Evidence and guidelines

  1. Primary source: Wai CT, Greenson JK, Fontana RJ et al. A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C. Hepatology 2003;38(2):518-526.
  2. European Association for the Study of the Liver. EASL Clinical Practice Guidelines on non-invasive tests for evaluation of liver disease severity and prognosis — 2021 update. J Hepatol 2021;75(3):659-689.

Have a follow-up question?

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