APRI (AST to Platelet Ratio Index): Explanation and Clinical Context The APRI score is a non-invasive index to predict the presence of liver fibrosis and cirrhosis, originally validated in patients with chronic hepatitis C.
It is calculated using the formula: [(AST / Upper Limit of Normal AST) / Platelet Count (10^9/L)] × 100.
Lower values (<0.5) indicate minimal or no fibrosis, intermediate values (0.5–1.5) suggest possible moderate fibrosis, and higher values (>1.5) indicate significant fibrosis or cirrhosis.
This tool helps clinicians to stratify patients for further diagnostic evaluation, such as liver biopsy or elastography, and to guide management decisions in chronic liver disease.
Reference:
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):518-526. doi:10.1053/jhep.2003.50346