Aspartate aminotransferase
S-ASAT KL 1128
(in English S -AST)
Elevated concentrations of aspartate aminotransferase (AST) can occur in various conditions, such as heart attacks, leading to muscle damage. AST is an enzyme involved in amino acid metabolism, catalyzing the transfer of an amino group from aspartate to alpha-ketoglutarate, resulting in the formation of oxaloacetate and glutamate. The highest abundance of the AST enzyme is found in the heart muscle, liver, and skeletal muscle, but it is also present in red blood cells, kidneys, lungs, and pancreas.
Indications
The diagnosis of liver diseases, including the differential diagnosis of various hepatitis types based on the AST/ALT ratio. Additionally, using AST as an additional diagnostic test for muscular diseases and to identify myocardial infarction or other muscle-related damage.
Sample
0.5 mL of serum. Hemolysis causes incorrectly high S -AST levels.
Storage and delivery
The sample can be refrigerated for up to a week, but for longer storage, it should be kept frozen. Delivery at room temperature. Store refrigerated over the weekend.
Method
Photometric, in accordance with IFCC recommendation. Accredited method.
Turnaround time
1-2 weekdays
Reference ranges
| Age | Value (U/I) |
|---|---|
| children, 0 – 16 yrs | below 50 |
| 17 yrs | 15 – 35 |
| men, from 18 yrs | 15 – 45 |
| women, from 18 yrs | 15 – 35 |
Interpretation of results
Due to the presence of the aspartate aminotransferase (AST) enzyme in various tissues, an elevated AST value is considered a rather non-specific finding. In acute viral hepatitis, the AST value can increase by up to tenfold compared to the reference values, with the highest elevations observed in toxic and ischemic hepatitis. Notably, the AST value rises before jaundice appears in these conditions. When compared to ALT, AST is usually less elevated in cases of viral, drug-induced, and autoimmune hepatitis. However, in severe toxic hepatitis and alcoholic hepatitis, the AST value rises more significantly than the ALT value.
The AST/ALT ratio, calculated by comparing the levels of these two aminotransferase enzymes, can help determine the cause of liver inflammation:
An AST/ALT ratio below 1 indicates viral, drug-induced, or autoimmune hepatitis.
An AST/ALT ratio greater than 1 indicates severe toxic hepatitis.
An AST/ALT ratio above 2 indicates alcoholic hepatitis.
Moreover, the AST value increases in conditions such as myocardial infarction, pulmonary embolism, pancreatitis, muscular dystrophies, muscle strain, and hemolytic states. In these instances, the increase in ALT value is more gradual, resulting in a high AST/ALT ratio.
The reference values for adults align with the joint Nordic NORIP study.
Inquiries
martin.tornudd@milalab.fi
Last update 8.8.2023
