Alanine aminotransferase (AST or GOT) test
Liver Function Panel
Definition and Patient Education
This topic is for general information about AST test but it includes sections for medical technicians and medical lab specialist with links referring to these sections. If you want to read the technical sections, follow the links that refer to it.
Formal name: Aspartate Aminotransferase (AST)
Also known as: Serum Glutamic-Oxaloacetic Transaminase; SGOT; GOT; Aspartate Transaminase.
2) What is the AST?
We all hear about liver enzymes that are tested to detect liver diseases. These enzymes are:-
- ALT or Alanine Aminotransferase enzyme – previously known as Serum Glutamic-Pyruvic Transaminase; SGPT; GPT.
- AST or Aspartate Aminotransferase (AST) – previously known as Glutamic-oxaloacetic transaminase (GOT)
AST is present with a large amount in the liver, kidneys, cardiac muscle, and skeletal muscle and with small amounts in the brain, pancreas, and lungs. ALT found principally in the liver with only small amounts in other organs.
When the liver cell damaged due to virus infection, for example, these enzymes will exit from the cell to the blood circulation and thus their presence in high amounts in the blood indicate liver cell damage. Although AST and ALT are raised due to liver damage, ALT is more specific for detecting liver damage than AST because it found principally in liver cells.
We talk before about ALT test. Click here to read about it.
To diagnose liver disease, AST cannot be requested alone. WHY? Because, as we said, AST is present with large amount in many parts of the body and hence its level can be elevated in many cases. This means any factor that cause damage to the liver cells, the heart muscle cells, the kidneys or the skeletal muscle cells can increase the AST Level. Therefore, AST increases in the following conditions, for example:-
- Liver damage due to virus infection, cirrhosis, alcohol hepatitis.
- Carbon tetrachrolide poisoning.
- Myocardial infarction
- Muscular dystrophy
- Crushed muscle injuries.
- Acute pancreatitis.
- Acute burns, surgery.
- Even it increases in pregnancy, a shot or injection of medicine into muscle tissue, or even strenuous exercise may increase AST levels.
This means that AST level is not specific for liver damage because it can be increased even in muscle injuries, so, how could it used to diagnose liver disease?
ANSWER: – AST can be requested along with ALT test and other tests, such as Total protein, albumin, Alkaline phosphatase (ALP), bilirubin to help in determining which form of liver disease is present. In addition to its ability for differentiating causes of liver injury, it can recognize if the increased levels come from another source or not, such as heart or muscle injury. How? When ALT and AST tests are ordered together, an AST/ALT ratio is calculated. This ratio can differentiate the cause of the AST increased level; if it is from the liver or another source. For example, usually ALT is higher than AST, so, AST/ALT ratio is less than (1.0). However, there are some conditions at which it may be more than one, such as cirrhosis and in the first day or two of acute hepatitis or injury from bile duct obstruction. Also, it becomes more than 2.0 in alcoholic liver disease.
However, AST/ALT ratio doesn’t mean any thing when AST and ALT levels are normal. Also, it is specific for certain conditions especially for liver diseases because it may be more than one in liver disease and heart attack. So, it is more relevant to use this ratio in diagnosis of liver diseases.
After you know these information, you can conclude that ALT is more specific in diagnosis of liver disease.
3) Why it is required?
To detect and investigate liver is damage and to monitor the patient who take drugs that may cause damage to liver cells such as antiretroviral drugs which is used to control HIV infections. In addition, it is required to monitor the risk of hepatitis virus infection if you are infected.
Also, AST is ordered in case of a patient with myocardial infraction, or the heart diseases because it is present in heart muscle cells with large amount.
4) When should you get tested?
When the physician thinks that you have symptoms of a liver disorder such as:-
- Weakness, fatigue
- Loss of appetite
- Nausea, vomiting
- Abdominal swelling and/or pain
- Dark urine, light-colored stool
Also, the physician requests this test to follow up the effect of the drug you take for treatment of hepatitis infection or when the patient has an increased risk for liver disease since many people with mild liver damage will have no signs or symptoms. For example:-
- Persons who have a history of known or possible exposure to hepatitis viruses.
- People drink alcohols.
- A family history of liver disease.
- Persons who take drugs that might damage the liver
- Obese or diabetic patients.
5) What are the needed preparations before the test?
No special preparations are required before testing.
This is section for medical technicians or medical lab specialists. If you want to read it, read in Required sample for AST test in lab (coming soon).
This is section for medical technicians or medical lab specialists. If you want to read it, read in Procedure of AST test in lab (coming soon).
This is section for medical technicians or medical lab specialists. If you want to read it, read in Sources of errors in AST test in lab (coming soon).
This is section for medical technicians or medical lab specialists. If you want to read it, read in Quality control of AST test in lab (coming soon).