How accurate is the APRI?

For cirrhosis (F4), APRI has an AUROC of 0.77 using a cutoff of 2.0 (sensitivity 48%, specificity 94%). For significant fibrosis (F2-F4), AUROC is 0.76 using a cutoff of 0.5. It performs best at the extremes (ruling in or ruling out) with an indeterminate zone in between.

When should I use APRI vs FIB-4?

Use both together. FIB-4 generally has better discrimination (AUROC 0.85), especially in patients over 35. APRI has the advantage of requiring only 2 values. If both agree, confidence is higher; if they disagree, further testing is warranted.

Does the APRI work for fatty liver disease (MASLD)?

APRI performs less well in MASLD/NAFLD compared to viral hepatitis. For MASLD, the NFS (NAFLD Fibrosis Score) or FIB-4 are preferred non-invasive tests. FibroScan is the best non-invasive option.

What does a low platelet count mean for fibrosis?

Thrombocytopenia (<150 ×10⁹/L) in liver disease often reflects portal hypertension or hypersplenism, both indicators of advanced fibrosis or cirrhosis. This is why platelets are central to the APRI formula.

Should I use my lab's AST ULN or a standard value?

Use your specific laboratory's upper limit of normal, as it varies by assay and lab (typically 35-40 U/L). Using an incorrect ULN will systematically shift your APRI score.

How often should APRI be rechecked?

For chronic liver disease under treatment, recheck every 6-12 months. Sustained improvement (especially with HCV cure or HBV suppression) may indicate fibrosis regression.

APRI Score Calculator (AST to Platelet Ratio Index)

Calculate the APRI score for non-invasive liver fibrosis assessment. Also compares FIB-4 and AST:ALT ratio for broader liver-fibrosis review.

⚠️ Medical Disclaimer: APRI and FIB-4 are non-invasive screening tools for liver fibrosis. They do not replace liver biopsy or elastography for definitive staging. Results must be interpreted by a hepatologist.

AST (SGOT)

U/L

AST Upper Limit of NormalLab-specific (typically 35-40)

U/L

Platelet Count

×10⁹/L

ALT (SGPT)For FIB-4 and De Ritis ratio

U/L

AgeFor FIB-4 calculation

years

Liver Disease Etiology

APRI Score

1.08

Indeterminate

FIB-4 Index

3.23

Indeterminate — further workup

APRI

1.08

((AST 65 / ULN 40) / Platelet 150) × 100. Consider elastography or specialist follow-up if clinically appropriate

FIB-4

3.23

(Age × AST) / (Platelet × √ALT). Indeterminate — further workup

De Ritis Ratio (AST:ALT)

1.44

May suggest cirrhosis or non-hepatic source

APRI Classification

Indeterminate

Consider elastography or specialist follow-up if clinically appropriate

Platelet Count

150 ×10⁹/L

Normal (150-400 ×10⁹/L)

AST/ULN Ratio

1.6

Mildly elevated or normal

APRI Interpretation Thresholds

APRI Score	Interpretation	Typical Follow-up Context
<0.5	No significant fibrosis (F0-F1)	Routine monitoring or repeat risk assessment later
0.5–1.5	Indeterminate	Consider elastography or specialist follow-up if clinically appropriate
1.5–2.0	Significant fibrosis likely (F2-F3)	More definitive staging is usually warranted
≥2.0	Cirrhosis likely (F4)	High-risk range; confirm with full clinical evaluation

Fibrosis Assessment Methods Comparison

Test	Formula	Pros	Cons	Accuracy
APRI	(AST/ULN) / Platelet count	Simple, 2 values	Less accurate for intermediate fibrosis	AUROC 0.77 for cirrhosis
FIB-4	(Age × AST) / (Platelet × √ALT)	Better discrimination	Age-dependent	AUROC 0.85 for fibrosis
FibroScan (TE)	Transient elastography (kPa)	Direct measurement	Requires equipment; affected by BMI	AUROC 0.90 for cirrhosis
Liver Biopsy	Histological staging	Gold standard	Invasive, sampling error, costly	Reference standard

APRI Performance by Etiology

Etiology	APRI Cutoffs	Notes
Hepatitis C (HCV)	<0.5 = no fibrosis, >1.5 = cirrhosis	Most validated for HCV; WHO recommends APRI in resource-limited settings
Hepatitis B (HBV)	Same cutoffs; less validated	FIB-4 may be superior; combine with HBV DNA levels
MASLD/NAFLD	Less reliable; use FIB-4 or NFS	APRI underperforms in metabolic liver disease
Alcoholic liver disease	Elevated AST common; less specific	AST:ALT ratio >2 in alcoholic disease may confound

Planning notes, formulas, and examples

About the APRI Score Calculator (AST to Platelet Ratio Index)

The APRI Score Calculator computes the AST to Platelet Ratio Index for non-invasive review of liver fibrosis risk. It also calculates FIB-4 and the AST:ALT ratio so the result can be reviewed as part of a broader liver-fibrosis worksheet rather than as a single isolated score.

APRI was developed by Wai et al. as a simple, widely accessible fibrosis marker, especially in chronic hepatitis C. Because it uses only AST and platelet count, it remains useful in settings where elastography or biopsy are not immediately available.

This page is best read as a fibrosis triage tool. Low and high scores are often the most informative, while indeterminate scores usually need elastography, specialist follow-up, or other confirmatory assessment before advanced fibrosis is ruled in or ruled out.

When This Page Helps

APRI uses routine lab values that are available almost everywhere, making it a practical first-pass fibrosis screen. Showing APRI alongside FIB-4 helps frame whether the result looks reassuring, indeterminate, or concerning enough to justify more definitive follow-up such as elastography.

How to Use the Inputs

Enter your AST (SGOT) level from blood work.
Enter the AST upper limit of normal for your laboratory (usually 35-40 U/L).
Enter your platelet count in ×10⁹/L.
Enter ALT for FIB-4 and De Ritis ratio calculation.
Enter your age for FIB-4 calculation.
Select the underlying liver disease etiology.
Review APRI, FIB-4, and De Ritis ratio with interpretations.

Formula used

APRI = ((AST / AST Upper Limit of Normal) / Platelet Count (×10⁹/L)) × 100
FIB-4 = (Age × AST) / (Platelet Count × √ALT)
De Ritis Ratio = AST / ALT

APRI Cutoffs: <0.5 = no significant fibrosis, 0.5-1.5 = indeterminate, ≥1.5 = significant fibrosis/cirrhosis, ≥2.0 = cirrhosis
FIB-4 Cutoffs: <1.45 = low risk, 1.45-3.25 = indeterminate, >3.25 = advanced fibrosis

Example Calculation

Result: APRI = 1.08 (Indeterminate), FIB-4 = 1.52 (Indeterminate), De Ritis = 1.44

With AST 65 U/L (1.625× ULN) and platelets 150, APRI is 1.08, falling in the indeterminate range. FIB-4 of 1.52 also falls in the indeterminate zone. Both scores suggest further workup (FibroScan or biopsy) is needed.

Tips & Best Practices

Always use your lab-specific AST upper limit of normal — it varies by assay (35-40 U/L is common).
Check that your platelet count is in ×10⁹/L (same as ×10³/µL); convert if needed.
An AST:ALT ratio > 2 suggests alcoholic liver disease and may confound APRI interpretation.
Acute hepatitis flares dramatically increase AST and falsely elevate APRI — recheck when stable.
If APRI and FIB-4 are discordant, proceed to FibroScan or specialist evaluation.

WHO Recommendations for APRI

The World Health Organization guidance for chronic hepatitis B and C recommends APRI as the preferred non-invasive test in resource-limited settings where FibroScan is not available. An APRI >2.0 is recommended as the cutoff for cirrhosis, and APRI <0.5 for ruling out significant fibrosis, with intermediate values requiring further assessment when possible.

The FIB-4 Index

FIB-4 was developed from the HALT-C trial and incorporates age, AST, ALT, and platelet count. It has been validated in multiple liver disease etiologies and generally outperforms APRI, particularly for distinguishing advanced fibrosis (F3-F4). The combination of APRI and FIB-4 results in better classification than either alone.

From Non-Invasive Tests to Next-Step Decisions

In modern hepatology, non-invasive fibrosis assessment is mainly used to decide who can be reassured, who should get elastography or specialist review, and who may already be in a high-risk fibrosis range. The page should be read as a triage aid rather than a stand-alone fibrosis diagnosis.

Sources & Methodology

Last updated: March 27, 2026

Methodology

This page calculates APRI as "((AST / AST upper limit of normal) / platelet count) × 100", then shows the result alongside FIB-4 and the AST:ALT ratio so the liver-fibrosis screen can be reviewed as a bundle rather than as a single score. The score bands are presented as non-invasive triage ranges that help separate low, indeterminate, and higher-risk fibrosis patterns.

The result is intended for fibrosis risk stratification rather than for definitive fibrosis staging. APRI performs best at the low and high ends, while indeterminate values usually need elastography, specialist review, or other follow-up before advanced fibrosis is confirmed or excluded.

Sources

A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C (Hepatology) — Original APRI publication by Wai et al.
Guidelines for the prevention, care and treatment of persons with chronic hepatitis B infection (World Health Organization) — WHO guidance discussing APRI and other non-invasive fibrosis tools in resource-limited settings.

Frequently Asked Questions

For cirrhosis (F4), APRI has an AUROC of 0.77 using a cutoff of 2.0 (sensitivity 48%, specificity 94%). For significant fibrosis (F2-F4), AUROC is 0.76 using a cutoff of 0.5. It performs best at the extremes (ruling in or ruling out) with an indeterminate zone in between.