APRI Score Calculator

APRI Score Calculator for Gastroenterology. Two cut-offs anchor interpretation in HCV. For significant fibrosis, APRI <0.5 makes it unlikely (high negative predictive value) while >1.5 makes it likely; for cirrhosis, <1.0 argues against and >2.0 argues for. Values in the intermediate zone (roughly 0.5–1.5) are indeterminate and should prompt confirmatory testing such as transient elastography or biopsy rather than a firm conclusion. A high APRI supports staging-driven action (endoscopic variceal screening, HCC surveillance, treatment prioritization); a low APRI can safely defer invasive workup. The score classifies rather than measures, so a single number should be paired with clinical context, not treated as a fibrosis stage.

How this calculator works

APRI (AST to Platelet Ratio Index) is a two-variable arithmetic estimate of liver fibrosis: APRI = [(AST ÷ AST upper limit of normal) ÷ platelet count in 10^9/L] × 100. Because advancing fibrosis tends to raise AST while lowering the platelet count (through portal hypertension and reduced thrombopoietin), the ratio amplifies both signals in the same direction. Only two routine labs are needed, so no imaging, cost, or specialist input is required; the laboratory-specific AST ULN (commonly 40 U/L, but use your own lab's value) is essential to the calculation.

When to use this calculator

APRI was derived and validated in treatment-naive chronic hepatitis C to identify significant fibrosis (Ishak ≥3, roughly METAVIR ≥F2) and cirrhosis, and the WHO 2014 HCV guidelines endorsed it as a low-cost triage tool where transient elastography or FibroTest are unavailable, particularly in resource-limited settings. It is best used to rule cirrhosis in or out and to prioritize who needs further staging. It performs less well in chronic hepatitis B and should not be relied on in NAFLD/NASH (FIB-4 or elastography are preferred there), nor in acute hepatitis, hemolysis, thrombocytopenia from other causes, or after antiviral cure when AST normalizes.

Inputs used

  • AST
  • AST upper limit of normal
  • Platelet count

Clinical interpretation

Two cut-offs anchor interpretation in HCV. For significant fibrosis, APRI <0.5 makes it unlikely (high negative predictive value) while >1.5 makes it likely; for cirrhosis, <1.0 argues against and >2.0 argues for. Values in the intermediate zone (roughly 0.5–1.5) are indeterminate and should prompt confirmatory testing such as transient elastography or biopsy rather than a firm conclusion. A high APRI supports staging-driven action (endoscopic variceal screening, HCC surveillance, treatment prioritization); a low APRI can safely defer invasive workup. The score classifies rather than measures, so a single number should be paired with clinical context, not treated as a fibrosis stage.

Worked example

A hepatitis C patient has AST 90 U/L (lab ULN 40) and platelets 100 × 10^9/L. AST/ULN = 90/40 = 2.25; divided by 100 = 0.0225; × 100 = APRI 2.25. Because this exceeds the 2.0 cirrhosis cut-off, cirrhosis is likely and the patient warrants variceal screening and HCC surveillance. Contrast: AST 45, platelets 250 → (45/40)/250 × 100 = 0.45, below 0.5, arguing against significant fibrosis.

Limitations and safety notes

Accuracy is best at the extremes; a large share of patients fall in the indeterminate middle where APRI cannot classify, and sensitivity for cirrhosis is limited, so a low score does not exclude it. Any process that independently raises AST (alcohol, hemolysis, muscle injury, drug hepatotoxicity) or drops platelets (immune thrombocytopenia, hypersplenism, chemotherapy) will distort the result away from true fibrosis burden. It underperforms outside chronic hepatitis C, notably in hepatitis B and NAFLD, and loses validity once antiviral therapy normalizes AST, so it should not be used to track regression after cure.

Frequently asked questions

What AST upper limit of normal should I enter?

Use your own laboratory's AST ULN because the formula normalizes AST to it; the original study and many calculators default to 40 U/L, but a lab reporting a different ULN will shift the score, so match the value to the assay that produced the AST result.

Does APRI work for fatty liver disease (NAFLD/NASH)?

Not well. APRI was developed and validated in chronic hepatitis C. For NAFLD/NASH, FIB-4 or transient elastography (with VCTE-based scores) are the preferred noninvasive tools and outperform APRI for detecting advanced fibrosis.

What do the numbers actually mean?

In HCV, APRI <0.5 makes significant fibrosis unlikely and >1.5 makes it likely; for cirrhosis, <1.0 argues against and >2.0 argues for. Values between these thresholds are indeterminate and warrant confirmatory testing such as elastography or biopsy.

Can I use APRI to confirm treatment worked after HCV cure?

No. AST typically normalizes after successful antiviral therapy, which lowers APRI independent of any true change in fibrosis, so a post-treatment score does not reliably reflect residual scarring or regression.

How does APRI compare with FIB-4?

Both use routine labs and are inexpensive. FIB-4 adds age and ALT and generally performs comparably or slightly better for advanced fibrosis across several etiologies, so many guidelines use them together, but APRI remains a WHO-endorsed option where resources are constrained.

References

  • Wai CT, Greenson JK, Fontana RJ, Kalbfleisch JD, Marrero JA, Conjeevaram HS, Lok AS. A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C. Hepatology. 2003;38(2):518-526. PMID: 12883497.
  • World Health Organization. Guidelines for the screening, care and treatment of persons with hepatitis C infection. Geneva: WHO; 2014.
  • Lin ZH, Xin YN, Dong QJ, Wang Q, Jiang XJ, Zhan SH, Sun Y, Xuan SY. Performance of the aspartate aminotransferase-to-platelet ratio index for the staging of hepatitis C-related fibrosis: an updated meta-analysis. Hepatology. 2011;53(3):726-736. PMID: 21319189.

Editorial review and citation methodology

Reviewed by the Quick Medical Calculator Editorial Team. Last reviewed: April 18, 2026. The review checks calculator inputs, intended population, interpretation, limitations, and source alignment.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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