What are the aminotransferases (Alanine Transaminase (ALT) and Aspartate Transaminase (AST)) tests?

From the Guidelines

Aminotransferase tests, including Alanine Transaminase (ALT) and Aspartate Transaminase (AST), are blood tests that measure liver enzyme levels to evaluate liver function and detect liver damage or disease. These tests are crucial in assessing liver health, as elevated levels of ALT and AST can indicate liver injury or disease, such as hepatitis, fatty liver disease, or medication-induced liver injury 1.

Key Points About Aminotransferase Tests

• ALT is found predominantly in the liver, making it more specific for liver damage, while AST is found in the liver, heart, muscles, kidneys, and brain 1.
• Normal ALT levels range from 29 to 33 IU/L (0.48-0.55 mkat/L) in men and 19 to 25 IU/L (0.32-0.42 mkat/L) in women, as stated in the most recent study 1.
• Elevated levels of ALT and AST can be classified as mild, moderate, or severe, with moderate and severe elevations indicating significant liver damage 1.
• The ratio of AST to ALT can provide diagnostic clues, with a ratio greater than 2:1 often suggesting alcohol-related liver disease.

Clinical Application of Aminotransferase Tests

• Doctors typically order these tests as part of a comprehensive metabolic panel during routine check-ups or when liver disease is suspected 1.
• Abnormal results should be interpreted in the context of all clinical information, and further diagnostic evaluation should be directed toward establishing a diagnosis based on the specific clinical scenario of the individual patient 1.
• In patients with elevated serum aminotransferases, common hepatic diseases should be excluded with noninvasive serologic tests, and additional testing or observation should be based on the clinical scenario 1.

From the Research

Aminotransferases Tests

• The aminotransferases tests, also known as Alanine Transaminase (ALT) and Aspartate Transaminase (AST) tests, are commonly used biomarkers for liver damage 2, 3.
• These tests are indicators of hepatocellular injury, and an increase in ALT and AST levels requires further investigations 3.
• ALT is considered the most specific marker for liver damage, as AST is also present in cardiac and skeletal muscle and in erythrocytes 2.

Purpose of the Tests

• The purpose of the ALT and AST tests is to diagnose and assess liver diseases, such as viral hepatitis, nonalcoholic fatty liver disease, and alcoholic liver disease 3.
• The tests are also used to monitor the outcome after treatment of each specific liver disease and to assess the prognostic outcome of liver diseases 3.
• Elevated AST levels have been associated with increased mortality from all-cause, liver disease, and liver cancer, and have been found to be a better predictor of mortality than ALT 4.

Interpretation of Results

• The normal ALT level ranges from 29 to 33 IU/L in males and 19 to 25 IU/L in females 3.
• Elevated ALT and AST levels require further investigations, including testing for viral hepatitis, assessment for nonalcoholic fatty liver disease and alcoholic liver disease, and screening for autoimmune hepatitis and other liver diseases 3.
• The results of the ALT and AST tests should be interpreted in conjunction with other clinical and laboratory findings to determine the underlying cause of liver damage 2, 3.

Future Developments

• New biomarkers of liver injury are being developed, which may complement or replace ALT and AST in the future 5.
• Low-cost point-of-care monitoring of ALT and AST is promising for faster decision making and diagnosis of acute liver injury, particularly in developing countries 6.