The health of your liver can be gauged through various blood tests, with those measuring liver enzyme levels offering valuable insights. Among these, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are routinely checked markers. These enzymes provide a window into the state of your liver, helping healthcare providers assess its condition.
What Are AST and ALT Enzymes?
Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are enzymes involved in amino acid metabolism. ALT is found predominantly in the liver, making it a more specific indicator of liver cell damage. AST, while also present in the liver, is found in other tissues, including the heart, skeletal muscles, kidneys, and red blood cells. When liver cells or other tissue cells are damaged, these enzymes can be released into the bloodstream, leading to elevated levels detectable by a blood test.
The Significance of the AST/ALT Ratio
Healthcare professionals often consider the ratio of AST to ALT, known as the De Ritis ratio. This ratio is calculated by dividing the AST value by the ALT value. Analyzing the AST/ALT ratio can provide specific clues about the type and cause of liver damage, helping differentiate between various liver conditions.
Interpreting Ratio Values and Related Conditions
A typical AST/ALT ratio in healthy individuals is around 0.7 to 1.2, meaning ALT levels are slightly higher or similar to AST levels. Most liver cell injuries show a greater increase in ALT than AST. Specific patterns in the ratio can point to different underlying conditions.
A ratio greater than 2:1 suggests alcoholic liver disease, such as alcoholic hepatitis or alcoholic cirrhosis. This elevated ratio can also be seen in patients with nonalcoholic steatohepatitis (NASH) who have developed cirrhosis, or in some cases of hepatitis C with cirrhosis.
Conversely, an AST/ALT ratio less than 1:1 is observed in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). This pattern occurs because ALT is more specific to liver damage from fat accumulation. In cases of acute viral hepatitis, the AST/ALT ratio is also less than 1. Extremely high levels of both AST and ALT, with varying ratios, indicate acute liver injury, such as drug-induced liver injury or severe acute viral hepatitis.
Factors Influencing the Ratio and Next Steps
Several factors beyond liver disease can influence AST and ALT levels, thereby affecting their ratio. Strenuous physical activity, muscle injury, certain medications, and hemolysis (the breakdown of red blood cells) can cause elevations. Intense exercise like weightlifting can increase AST and ALT.
An abnormal AST/ALT ratio warrants further medical evaluation by a healthcare professional. It is important not to self-diagnose based solely on this ratio, as it is just one piece of a larger diagnostic puzzle. Additional tests, such as imaging studies, viral markers, or a liver biopsy, are needed to determine a diagnosis and appropriate course of action.