Calculators · Gastroenterology & Hepatology · Formula
APRI (AST to platelet ratio index)
Also called AST platelet ratio
Non-invasive marker of significant fibrosis and cirrhosis in chronic viral hepatitis.
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Formula and scoring
APRI = (AST ÷ AST ULN) × 100 ÷ platelets (10⁹/L). WHO example: AST 82, ULN 40, platelets 90 → 2.28.
Exam and ward pearls
- WHO 2015 HBV guideline recommends APRI > 2 to identify cirrhosis where elastography is not available.
- High specificity, low sensitivity: a low APRI does not exclude cirrhosis.
When not to rely on it
- Derived in chronic hepatitis C; AST rises in alcohol use, muscle injury and acute hepatitis, which falsely raise APRI.
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):518-26. doi:10.1053/jhep.2003.50346 · PMID 12883497
- World Health Organization. Guidelines for the prevention, care and treatment of persons with chronic hepatitis B infection. Geneva: WHO; 2015. Chapter 4, Figure 4.1 and Table 4.3. Link
Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.