The AST-to-Platelet Ratio Index (APRI) is a non-invasive diagnostic tool primarily used in the assessment of hepatic fibrosis and cirrhosis in patients with chronic liver diseases, such as hepatitis C. The APRI calculator utilizes readily available laboratory values, specifically aspartate aminotransferase (AST) levels and platelet counts, to estimate the degree of liver fibrosis. This tool is particularly useful in settings where liver biopsy, the gold standard for diagnosing liver fibrosis, is contraindicated or not feasible due to its invasive nature and potential complications. The APRI score can help guide clinical decision-making regarding the need for further invasive testing or initiation of antiviral therapy. However, it should be noted that the APRI score may not be as accurate in patients with acute liver injury, non-hepatic causes of thrombocytopenia, or in those with normal or mildly elevated AST levels.