AST and ALT are two important enzymes that evaluate liver function. These tests help determine liver health and are used to diagnose liver diseases. These tests are often measured during routine blood tests. Both enzymes are found in liver cells and are released into the blood when these cells are damaged. High levels of AST and ALT may indicate liver damage or disease.

What is AST (Aspartate Aminotransferase)?

AST is an enzyme that catalyzes the reaction between aspartate and alpha-ketoglutarate. It is normally found in the liver, heart, muscles, kidneys, and brain. However, AST levels are often used to evaluate liver disease. When liver cells are damaged, AST is released into the blood, which shows up as high levels in blood tests. Elevated AST levels can indicate diseases of the heart, skeletal, and kidneys, as well as the liver.

What is ALT (Alanine Aminotransferase)?

ALT is an enzyme that catalyzes the reaction between alanine and alpha-ketoglutarate. ALT is found primarily in liver cells and is associated with the liver. Therefore, an ALT test provides more specific information about liver health. Elevated ALT levels often indicate liver damage and may indicate liver diseases such as hepatitis, cirrhosis, or alcoholic liver disease.

High AST and ALT Tests

• High AST : Elevated AST levels can be a symptom of health problems other than liver disease. Heart attack, muscle disease, pancreatitis, alcohol use, and damage to other organs can all increase AST levels. Therefore, an AST test alone is not sufficient to definitively diagnose liver disease.
• Elevated ALT : Elevated ALT levels generally indicate liver damage. ALT is a more specific marker than AST because it is specific to liver cells. Elevated ALT levels can be caused by factors such as hepatitis, liver inflammation, fatty liver disease, alcoholic liver disease, or medications.

AST/ALT Ratio

The AST/ALT ratio can be used to determine the type of liver disease. Normally, the AST/ALT ratio is close to 1. However, in some cases, this ratio can vary:

• Alcoholic liver disease : The ratio of AST to ALT may often be 2:1 or higher.
• Viral Hepatitis : ALT may be higher than AST.
• Cirrhosis and Liver Failure : In these diseases, AST and ALT are usually elevated, although the ratios may differ.

Interpretation of Results

• Normal Levels : AST and ALT levels are generally considered to be between 10 and 40 U/L. However, these values ​​may vary depending on the methods and reference ranges used by the laboratory.
• High Levels : High AST and ALT levels can indicate liver cell damage. However, elevated AST and ALT levels can indicate not only liver disease but also conditions such as muscle and heart disease.
• Low Levels : Low AST or ALT levels usually indicate no health problems. However, in some cases, vitamin deficiencies or genetic disorders can also cause low levels.

Limits of AST and ALT Testing

While helpful in determining liver health, these tests alone are not sufficient to provide a definitive diagnosis. They must be supported by other blood tests and imaging studies. Additionally, certain medications, alcohol use, excessive exercise, or muscle injuries can affect the levels of these enzymes.

AST and ALT tests are important tools for assessing liver health and detecting diseases in their early stages. Liver diseases often have no symptoms in their early stages, so regular testing and checkups are critical to maintaining liver health.