AST in the blood: what is it, Norma

AST – an indicator of biochemical blood analysis, which displays the quantity of the enzyme aspartate aminotransferase (AST) in the peripheral blood. In a healthy person this enzyme is concentrated inside liver, heart, muscle and kidney cells, and blood him a little bit. The destruction of these cells as a result of various pathological processes is the release of the enzyme into the blood and the increase of its concentration in it. For determining the condition of the cells of these organs and uses this measure.

A blood test for AST. What is it?

Analysis of most often prescribed for the establishment of the fact of destruction of liver cells or cardiac muscle. Only in these cases in the blood will increase the activity of the enzyme AST. Often use this study for the differential diagnosis of various symptoms. If, for example, chest pain is not accompanied by an increase in AST, it is likely that cardiac muscle was not damaged, and myocardial cells is not destroyed.

It is important to remember that the activity of AST depends on the degree of destruction of cells – the higher it is, the higher the level of the enzyme. In addition, the activity of AST depends on the moment of blood sampling from the beginning of the destructive process in the cells. The more time that passed, the less will be the level of AST. Indications for determination of AST in the blood:

  • Acute or exacerbation of chronic diseases of the cardiovascular system, liver or kidneys.
  • Poisoning by drugs, toxins of viruses or bacteria, intoxication syndrome. Analysis allows you to determine whether the destruction of the liver cells under these conditions. This, in turn, will help determine the tactics of treatment.
  • Renal, cardiac or hepatic failure.
  • Differential diagnosis of jaundice. The increase in AST levels in this state will speak in favor of the hepatic type of jaundice.
  • Ascites (accumulation of fluid in the abdominal cavity) or portal hypertension (increased pressure in liver blood vessels).
  • The signs of stagnation of bile, biliary dyskinesia, of the presence of stones in the gallbladder or ducts.
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  • Oncologic pathology with the formation of metastases.
  • Injury in which the probability of damage to the tissues of heart, liver or kidneys.
  • Reception toxic to the liver or kidneys of drugs (antibiotics, chemotherapy). At the increase of AST in patients receiving these drugs, a patient need to transfer to a different group of drugs.
  • Control of therapy of liver disease.

Norma AST in the blood in adults and children

Age category of the patients

Normal levels of AST

In children from birth to year

year to 4 years

with 4 to 7 years

from 7 to 13 years

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from 13 to 18 years

Not more than 58 U/l

Not more than 59 U/l

No more than 48 U/l

No more than 44 U/l

Not more than 39 U/l

Men (over 18)

Not more than 40 U/l

Women (over 18)

Up to 32 U/l

It should be noted that in pregnant women the rate can be reduced, so the diagnosis of diseases of the liver or heart when pregnancy is combined with other tests. Intense exercise, intramuscular or intravenous injection before the analysis could falsely increase the AST.

In some cases, the AST level can be upgraded?

  • Acute myocardial infarction, especially immediately after its occurrence. Activity of the enzyme, it is possible to draw conclusions about the recovery of the heart muscle. The lower the level of AST, the better is the recovery process.
  • Bruises of the heart with myocardial injury.
  • Myocarditis (inflammation of heart muscle). It is important to remember that the analysis is not differentiarum the form of myocarditis (autoimmune, infectious), it just shows that heart muscle cells are damaged.
  • Hepatitis (inflammation of liver tissue) of any kind (viral, toxic).
  • Intoxication (alcohol, drugs, infection), accompanied by damage of cells of liver, kidney or heart.
  • Myositis (inflammation muscle tissue) of any origin.
  • Stagnation of bile in the bile ducts (cholestasis) caused by the presence of stones in the bile duct, neoplasms, congenital anomalies. The latter option is more common in children than adults. Children have the anomalous excesses of the gallbladder, abnormal shape (hourglass), diverticula and so on.
  • Portal hypertension (increased pressure in liver blood vessels) and impaired blood flow in the liver.
  • Cirrhosis of the liver. The increase of AST is observed only in the early stages, when the body still remained intact plots. When the liver is completely replaced by connective tissue (sclerosis), the AST level is sharply reduced.
  • Cancer of the liver or biliary tract, and liver metastases while the primary lesion elsewhere in the body.

How to prepare for the analysis?

Any biochemical analysis to avoid a false result requires special preparation of the patient:

  • Blood sampling for analysis must be conducted on an empty stomach. It is advisable that the patient abstain from eating for 8 – 12 hours before the study. You can drink only water (non-carbonated and unsweetened), otherwise the test result may be false positive.
  • It is not recommended to engage in physical exercise, this can cause damage to muscle tissue and increase of AST out of touch with the disease. Even climbing the stairs above the 3rd floor before donation can skew the results, that is why clinical and biochemical laboratory in the clinics must be located on the ground floor.
  • Drinking alcohol and Smoking before the test can cause damage to a certain number of liver cells and false results. In this case, the increase in AST will speak about the toxic effects of alcohol on the liver, but not about her illness.
  • Taking certain medicines need to cancel 2 weeks before analysis. These include opiates, sulfonamides, vitamins B6 and K, anti-TB drugs and aspirin.
  • Intake of fatty foods before the study can also distort the results of the analysis.
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