APRI — AST-to-Platelet Ratio Index for Liver Fibrosis

The APRI (AST-to-Platelet Ratio Index) is a non-invasive serum-based index for estimating the degree of liver fibrosis and cirrhosis in patients with chronic liver disease, particularly chronic hepatitis C and hepatitis B. APRI is calculated as (AST/ULN_AST × 100) / platelet count (10⁹/L) and provides a simple, inexpensive alternative to liver biopsy for fibrosis staging when combined with clinical context. Endorsed by WHO guidelines for resource-limited settings.