APRI Calculator
Calculate APRI score from AST, platelet count, and AST upper limit to screen for liver fibrosis and cirrhosis.
What Is the APRI Score?
The AST to Platelet Ratio Index (APRI) is a non-invasive marker used to estimate the likelihood of hepatic fibrosis and cirrhosis without liver biopsy. It combines aspartate aminotransferase (AST) and platelet count from routine blood work. For related liver assessments, see the AST ALT Ratio Calculator and Albumin Globulin Ratio Calculator.
APRI Formula
$$APRI = \frac{AST / AST_{ULN}}{Platelets} \times 100$$
AST is measured in IU/L, platelets in 10⁹/L, and the AST upper limit of normal (ULN) is typically 40 IU/L. Higher scores suggest greater fibrosis burden.
Interpreting APRI Thresholds
An APRI below 0.5 makes significant fibrosis unlikely. A score of 0.7 or higher suggests possible significant fibrosis, while 1.0 or higher is associated with cirrhosis in hepatitis C cohorts. Scores of 2.0 or above strongly indicate advanced disease.
Frequently Asked Questions
What is a normal APRI score?
APRI below 0.5 is generally considered low risk for significant fibrosis. There is no single normal value — interpretation depends on clinical context and the threshold being applied.
What AST upper limit should I use?
Most laboratories and guidelines use 40 IU/L as the AST upper limit of normal. You can adjust this if your lab uses a different reference range.
Can APRI replace a liver biopsy?
APRI is a screening tool, not a definitive diagnosis. Biopsy or elastography may still be needed to confirm fibrosis stage and guide treatment.
What conditions affect APRI?
Acute hepatitis, hemolysis, splenomegaly, and medications can alter AST or platelets independently of fibrosis, potentially skewing the index.
Is APRI validated for all liver diseases?
APRI was most extensively studied in chronic hepatitis C. It is also used in NAFLD and other chronic liver diseases, but performance varies by population.
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