From the Guidelines
A normal Aspartate Aminotransferase (AST) level on a Comprehensive Metabolic Panel (CMP) indicates that your liver is likely functioning properly. The typical normal range for AST is between 8 and 40 units per liter (U/L), though exact reference ranges may vary slightly between laboratories 1. AST is an enzyme found primarily in the liver, but also in heart, muscle, kidney, and brain tissues. When these tissues are damaged, AST is released into the bloodstream, causing elevated levels. Therefore, normal AST values suggest absence of significant liver cell damage or disease.
However, it's essential to consider the following points:
- AST should be interpreted alongside other liver enzymes like Alanine Aminotransferase (ALT) and other CMP components for a complete assessment of liver health.
- Even with normal AST levels, other abnormal values on the CMP might indicate health issues requiring further investigation.
- AST levels can temporarily rise after strenuous exercise or with certain medications, so context is crucial when interpreting results 1.
- In patients with elevated baseline serum ALT, an increase of ALT to ≥2x baseline should prompt an evaluation for possible causes including possible immune-mediated liver injury versus tumor progression 1.
In the context of real-life clinical medicine, a normal AST level on a CMP is a good indicator of liver health, but it should not be considered in isolation. A comprehensive evaluation, including medical history, physical examination, and other diagnostic tests, is necessary to rule out any potential liver diseases or other health issues. According to the most recent and highest quality study available, a normal AST level is a positive indicator of liver health, but it requires careful interpretation in the context of the patient's overall clinical picture 1.
From the Research
Normal AST Levels on CMP
A normal Aspartate Aminotransferase (AST) level on a Comprehensive Metabolic Panel (CMP) indicates that the liver is functioning properly, and there is no significant liver damage or disease present.
Indications of Normal AST Levels
- Normal AST levels typically range from 0 to 40 units per liter (U/L) of blood, but this can vary slightly depending on the laboratory and the individual's overall health.
- A normal AST level does not necessarily rule out the presence of liver disease, as some liver conditions may not cause significant elevations in AST levels.
- Elevated AST levels can be caused by a variety of factors, including liver damage, muscle damage, and certain medical conditions, such as hepatitis or cirrhosis 2, 3.
Relationship Between AST and Liver Disease
- Chronic viral hepatitis, such as hepatitis B or C, can cause liver damage and elevate AST levels 4.
- Non-alcoholic fatty liver disease (NAFLD) is a common cause of liver disease, and AST levels can be used to help diagnose and monitor the condition 5.
- The AST to platelet ratio index (APRI) is a scoring system that can be used to predict the presence of advanced fibrosis and liver cirrhosis in patients with NAFLD, and a modified version of this index (m-APRI) has been shown to improve the accuracy of predictions 5.
Limitations of AST Testing
- AST testing is not specific to liver disease, and elevated levels can be caused by a variety of factors, including muscle damage and certain medical conditions.
- A normal AST level does not necessarily rule out the presence of liver disease, and further testing may be necessary to confirm a diagnosis.
- The use of AST levels in combination with other laboratory tests and clinical evaluations can help to provide a more accurate diagnosis and monitoring of liver disease 2, 3, 4, 5.