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Diagnostic Tests 2023

How to understand the TGO-AST exam: Aspartate Aminotransferase

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How to understand the TGO-AST exam: Aspartate Aminotransferase
How to understand the TGO-AST exam: Aspartate Aminotransferase

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

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

As a liver marker, AST is usually measured together with ALT, since it can be elevated in other situations, being nonspecific for this purpose. The reference value of the enzyme is between 5 and 40 U/L of blood, and may vary according to the 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 liver he alth, such as the measurement of gamma-glutamyl transferase (GGT), alkaline phosphatase (ALK) and, mainly ALT/TGP.

A high AST, or high TGO, may indicate:

  • Acute pancreatitis;
  • Acute viral hepatitis;
  • Alcoholic hepatitis;
  • Liver cirrhosis;
  • Liver abscess;
  • Primary liver cancer;
  • Major trauma;
  • Use of drugs that cause liver damage;
  • Heart failure;
  • Ischemia;
  • Infarction;
  • Burns;
  • Hypoxia;
  • Biliary tract obstruction such as cholangitis, choledocholithiasis;
  • Muscle injury and hypothyroidism;
  • Use of drugs 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 medication, such as paracetamol, or ischemic hepatitis, for example. On the other hand, decreased AST values may indicate vitamin B6 deficiency in the case of people who need dialysis.

Reason for Ritis

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 "Image" and when greater than 1 it is indicative of more serious injuries, 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 the exam is ordered

The TGO/AST blood test may be ordered by the doctor when it is necessary to evaluate the he alth of the liver, after observing that the person is overweight, has fatty liver or has signs or symptoms such as yellowing of the skin, pain in the right side of the abdomen or in case of pale stools and dark urine.

Other situations where it may also be useful to evaluate this enzyme is after the use of drugs that can damage the liver and to evaluate the liver of people who consume a lot of alcoholic beverages.

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