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Printed on 7/19/2026
For informational purposes only. This is not medical advice.
APRI is a non-invasive fibrosis marker that combines AST elevation relative to lab ULN and thrombocytopenia signal from platelet count. It is commonly used in chronic hepatitis and broader fibrosis triage pathways.
Formula: APRI = ((AST / AST ULN) x 100) / Platelets
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APRI requires three values from routine laboratory testing: AST (U/L) from the liver function panel, the upper limit of normal (ULN) for AST established by your specific laboratory (typically 35–40 U/L for most labs, but verify your lab's reference range), and platelet count (×10⁹/L or k/µL) from the complete blood count. Using your lab's specific ULN is important — do not use a fixed default value, as AST ULN varies by analyzer and population.
APRI = ((AST ÷ AST ULN) × 100) ÷ Platelet count. First, normalize AST by dividing by the lab's ULN, then multiply by 100, then divide by the platelet count in ×10⁹/L. Example: AST 80 U/L, ULN 40 U/L, platelets 120 ×10⁹/L — APRI = ((80/40) × 100) / 120 = 200 / 120 = 1.67. This indicates likely significant fibrosis. The formula was designed to be simple enough for calculation without a dedicated tool.
Fibrosis cutoffs (METAVIR F2-F4): APRI <0.5 = significant fibrosis unlikely (NPV ~80%); APRI 0.5–1.5 = indeterminate (requires second-line testing such as FibroScan); APRI >1.5 = significant fibrosis likely (PPV ~85%). Cirrhosis cutoffs: APRI <1.0 = cirrhosis unlikely (NPV ~92%); APRI >2.0 = cirrhosis likely (PPV ~89%). In resource-limited settings, APRI >2.0 in an HCV-infected patient with clinical signs of portal hypertension provides strong indirect evidence of cirrhosis.
Infectious disease physicians, WHO-implementing clinicians
WHO 2022 HCV Treatment Guidelines recommend APRI as the preferred non-invasive fibrosis test when FibroScan is unavailable. APRI requires only a basic metabolic panel and CBC — equipment available at virtually any clinic globally — making it the dominant fibrosis staging tool in global HCV elimination programs.
Hepatologists and gastroenterologists
While AASLD/AGA 2023 recommends FIB-4 as the first-line tool for NAFLD/MASLD, APRI serves as a valid alternative when FIB-4 is unavailable or as a complementary assessment. Combined FIB-4 + APRI concordance improves specificity for advanced fibrosis.
Hepatologists
APRI has been validated for HBV fibrosis staging in multiple Asian and African cohorts. Serial APRI monitoring in chronic HBV patients on antiviral therapy tracks fibrosis regression (falling APRI over time with effective viral suppression).
General practitioners in community settings
In practices without access to elastography or hepatology referral, APRI >2.0 with clinical signs (splenomegaly, thrombocytopenia, ascites) provides a clinically actionable estimate of cirrhosis that can guide urgent referral.
Global health clinicians and program managers
APRI is specifically endorsed in the 2022 WHO Guidelines for the Care and Treatment of Persons Diagnosed with Chronic Hepatitis C Virus Infection as the non-invasive staging tool of choice in settings without FibroScan access, making it the world's most widely implemented fibrosis staging method by patient volume.
APRI uses only two variables (AST and platelets) vs FIB-4's four (age, AST, ALT, platelets). This simplicity makes it faster to calculate manually and more accessible globally. However, for NAFLD/MASLD specifically, FIB-4 has higher AUROC (~0.85 vs ~0.77 for APRI) and is preferred by AASLD/AGA 2023.
The WHO 2022 HCV guidelines specifically recommend APRI (over FIB-4 or other tools) for HCV fibrosis staging where FibroScan is unavailable — the primary consideration being accessibility and cost. In high-income settings with FibroScan access, APRI has largely been superseded by FIB-4 and elastography.
Multiple systematic reviews and meta-analyses comparing APRI and FIB-4 in NAFLD cohorts consistently show FIB-4 has superior AUROC. Lin et al. (Ann Intern Med 2011) confirmed APRI AUROC ~0.77 for significant fibrosis in HCV, with lower performance in NAFLD (~0.73). Use APRI in NAFLD only when FIB-4 cannot be calculated.
AST ULN varies by laboratory analyzer, population, and institutional standards (typically 35–45 U/L). Using a wrong ULN directly affects the APRI value proportionally. In many electronic calculators, the default ULN is set to 40 U/L — verify this matches your lab before interpreting results in clinical decisions.
Like FIB-4, APRI divides by platelet count, so immune thrombocytopenia (ITP), drug-induced thrombocytopenia, chemotherapy-related bone marrow suppression, or hypersplenism from portal hypertension all inflate APRI independent of fibrosis severity. In thrombocytopenic patients with non-hepatic causes, use elastography instead.
AST elevation during acute hepatitis A, B, or C flares, or drug-induced liver injury, will transiently drive APRI into the high-risk zone even in patients without significant fibrosis. Calculate APRI only when transaminases are at the patient's chronic stable baseline, typically 4–8 weeks after resolution of an acute injury.
When both scores concordantly indicate high fibrosis risk (FIB-4 >2.67 AND APRI >1.5), the likelihood of true advanced fibrosis is higher than either test alone. Concordant low results (FIB-4 <1.30 AND APRI <0.5) have high negative predictive value. Discordant results (one high, one low) represent a gray zone requiring second-line testing.
Multiple studies in chronic HBV cohorts, predominantly in Asia and Africa where HBV burden is highest, have validated APRI for fibrosis staging with performance similar to HCV settings. Serial APRI in HBV patients on entecavir or tenofovir therapy shows APRI decline as fibrosis regresses, providing a practical monitoring tool in low-resource contexts.
APRI was developed by Wai et al. (Hepatology 2003) in 270 HCV patients. A systematic review by Lin et al. (Ann Intern Med 2011) across 40 studies found AUROC 0.77 for significant fibrosis and 0.83 for cirrhosis in HCV. WHO 2022 HCV Treatment Guidelines recommend APRI as the preferred non-invasive fibrosis test in resource-limited settings. AASLD/AGA 2023 MASLD Pathway recommends FIB-4 as the preferred first-line tool over APRI for NAFLD.
Higher APRI values generally indicate greater fibrosis likelihood, while lower values suggest lower probability of advanced fibrosis.
Use APRI for non-invasive fibrosis risk stratification when AST and platelets are available, especially in initial hepatology triage.
APRI can be distorted by acute hepatitis flares, lab-specific AST ULN definitions, and non-hepatic causes of thrombocytopenia.
For related assessments, see FIB-4, AST/ALT Ratio and MELD Score.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
April 21, 2026 · trust-baseline
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