What is AST in a Blood Test?
An AST blood test measures the amount of aspartate aminotransferase (AST) in your blood. AST is an enzyme found primarily in the liver, but also present in the heart, muscles, and other tissues. When these cells are damaged, AST leaks into the bloodstream, resulting in elevated levels. Therefore, an AST test is commonly used to assess liver health and detect potential liver damage or disease. It's often used in conjunction with other liver function tests like ALT (alanine aminotransferase) for a more comprehensive evaluation.
- Normal Levels: AST is typically present in low levels in the blood. The exact normal range can vary slightly depending on the laboratory.
- Elevated Levels: High AST levels can indicate liver damage, liver disease (such as hepatitis or cirrhosis), heart muscle damage (myocardial infarction), muscle damage (rhabdomyolysis), or other conditions.
- Low Levels: While less common, low AST levels might not necessarily indicate a problem but could warrant further investigation.
Why is an AST Test Performed?
Doctors order AST tests for various reasons, including:
- Diagnosing liver disease: AST is a key indicator of liver cell damage.
- Monitoring liver disease progression: Tracking AST levels helps assess the effectiveness of treatment.
- Detecting heart damage: Elevated AST can suggest a heart attack.
- Evaluating muscle damage: High levels can indicate muscle injury or disease.
AST and other Liver Function Tests
The AST test is often performed alongside other liver function tests, such as ALT, ALP (alkaline phosphatase), and bilirubin, to provide a more complete picture of liver health. This comprehensive assessment helps doctors distinguish between different types of liver damage and determine the underlying cause.
For instance, a significantly higher ALT level compared to AST may suggest alcoholic liver disease, while similar elevations in both may indicate viral hepatitis.
In summary: The AST blood test is a valuable tool for assessing liver health and detecting various health conditions characterized by cell damage. The interpretation of AST levels should always be done in conjunction with a complete medical history, physical examination, and other relevant tests.
