How to Understand the TGO-AST Exam: Aspartate Aminotransferase


The aspartate aminotransferase or oxaloacetic transaminase (AST or TGO) test is a blood test required to investigate lesions that compromise the normal functioning of the liver, such as hepatitis or cirrhosis, for example.

Oxaloacetic transaminase or aspartate aminotransferase is an enzyme present in the liver that is usually elevated when liver damage is more chronic, as it is located more internally in the liver cell. However, this enzyme can also be present in the heart and can be used as a cardiac marker, which can indicate infarction or ischemia.

As a liver marker, AST is usually measured together with ALT, as it may be elevated in other situations, being nonspecific for this purpose. O enzyme reference value is between 5 and 40 U/L of blood, which may vary by laboratory.

what does high AST mean

Although the AST/TGO test is not very specific, the doctor may order this test along with others that indicate the health of the liver, such as the dosage of gamma-glutamyltransferase (GGT), alkaline phosphatase (ALK) and, mainly, ALT/TGP. Learn more about the ALT exam.

Increased AST, or high TGO, may indicate:

  • Acute pancreatitis;
  • Acute viral hepatitis;
  • Alcoholic hepatitis;
  • Hepatical cirrhosis;
  • Liver abscess;
  • Primary liver cancer;
  • Major trauma;
  • Use of medicine that causes liver damage;
  • Cardiac insufficiency;
  • Ischemia;
  • Infarction;
  • Burns;
  • Hypoxia;
  • Obstruction of the biliary tract, such as cholangitis, choledocholithiasis;
  • Muscle injury and hypothyroidism;
  • Use of medications such as heparin therapy, salicylates, opiates, tetracycline, thorazine or isoniazid

Values ​​above 150 U/L usually indicate some liver damage and above 1000 U/L may indicate hepatitis caused by the use of medications, such as paracetamol, or ischemic hepatitis, for example. On the other hand, decreased AST values ​​may indicate vitamin B6 deficiency in people who need to undergo dialysis.


Ritis reason

The Ritis ratio is used in medical practice to assess the extent of liver damage and thus establish the best treatment for the situation. This ratio takes into account the values ​​of AST and ALT and when greater than 1 is indicative of more serious lesions, such as cirrhosis or liver cancer, for example. When less than 1, it can be indicative of the acute phase of a viral hepatitis, for example.

When is the exam requested

The TGO/AST blood test can be ordered by the doctor when it is necessary to assess the health of the liver, after observing that the person is overweight, has fat in the liver or has signs or symptoms such as yellowish skin color, pain on the right side of the abdomen or in case of pale stools and dark urine.

Other situations where it may also be helpful to assess this enzyme is after using medications that can damage the liver and to assess the liver of people who consume a lot of alcoholic beverages.

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