An AST (aspartate aminotransferase) sample measures the amount of this enzyme in the blood. AST is normally found in red blood cells, the liver, heart, muscle tissues, pancreas and kidneys. The level of AST in the blood is low under normal circumstances. Further AST is released into the bloodstream when body tissues or organs such as the heart or liver are sick or damaged. The amount of AST in the blood is directly related to the extent of the tissue damage. After serious damage is done, AST levels rise for 6 to 10 hours and remain high for around 4 days. The AST test can be carried out at the same time as a test for alanine aminotransferase (ALT). The ratio of AST to ALT can help to determine whether the liver or any other organ has been damaged and whether alcohol abuse has been one cause of the damage to the liver.
The AST test is carried out in order to check the condition of the liver and see whether it has been damaged. This test makes it possible to identify liver diseases, in particular hepatitis and cirrhosis. Liver diseases may cause symptoms such as pain in the upper part of the abdomen, nausea, vomiting and – sometimes – jaundice. The test can also be carried out in order to check whether treatment for liver disease has been successful. Other reasons may include finding out whether jaundice was caused by a blood disease or liver disease, or keeping track of the effects of cholesterol-lowering medications and other medications that may harm the liver.
High levels are seen in heart attack patients after a maximum of 2 days. ASAT levels are also elevated in patients with hepatitis, toxic liver damage, liver enlargement, myopathy and pulmonary embolism. The individual ASAT levels are related to muscle mass. Maximum physical activity causes an increase of 0.17-0.34 ukat/L. The contraceptive pill with oestrogen causes an increase of up to 0.17 ukat/L.