ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes that catalyze the transformation of the amino acids alanine and aspartate. These enzymes are mainly located inside the liver cells (hepatocytes). The determination of their activity (level) in the blood is a diagnostically important laboratory study that makes it possible to diagnose various pathologies of the liver.
How is the analysis performed?
The determination of the activity of ALT and AST in the blood of men is performed during biochemical analysis. For the study, blood is collected from the cubital vein in a volume of about 5-10 ml. Blood collection is performed by a medical specialist in a medical hospital with the obligatory observance of the rules of asepsis and antisepsis, aimed at eliminating the possibility of infection of the patient. The blood taken is placed in a clean tube, where it remains for a certain period of time necessary for the formation of a clot and the separation of the serum. The resulting serum is investigated in the laboratory. Usually, a special biochemical analyzer is used to determine the activity of the enzymes ALT and AST. To obtain a reliable result of the study, the patient must perform several simple preparatory measures:
- Blood should be donated on an empty stomach, so the fence is usually held in the morning (only non-carbonated mineral water or unsweetened tea is allowed for breakfast).
- The last meal is allowed 8 hours before the analysis, so a light dinner is usually possible on the evening before the test.
- A few days before putting blood on the activity of ALT and AST, the intake of fatty, fried foods, and also alcohol is excluded, since they significantly increase the functional load on the liver.
- On the day of the study, it is recommended to avoid excessive emotional and physical exertion; smoking is not recommended for several hours before donating blood.
The implementation of such recommendations, as well as carrying out the determination of the activity of the enzymes ALT and AST in the blood of a man with the help of a modern biochemical analyzer, allow obtaining reliable results of the study.
Normal indicators of the activity of the enzyme ALT in the blood of men should not exceed 45 U (unit of action) in 1 liter of blood, AST – 31 U. Knowledge of the normal values of the activity index of these liver enzymes allows the doctor to correctly interpret the results of the analysis.
Reasons for raising
ALT and AST are hepatic enzymes, so an increase in their activity indicates damage to the cell membranes of hepatocytes with the release of enzymes in the blood. This occurs in various pathologies of the liver, which includes:
- Acute viral hepatitis (viral hepatitis A, B, C, D, E).
- Chronic viral hepatitis B and C in the stage of clinical and laboratory exacerbation.
- Liver abscess – the formation of a limited cavity filled with pus, which usually occurs during the development of nonspecific pyogenic bacterial infection.
- Cirrhosis of the liver, characterized by the replacement of hepatocytes by connective tissue.
- Oncological process, accompanied by the formation of a malignant neoplasm in the liver parenchyma.
- Hepatonecrosis (death of a tissue site of various sizes) of the liver parenchyma, triggered by various causes, including severe viral hepatitis, an autoimmune process, severe blood circulation disorders.
- Toxic liver damage, developing on the background of systematic alcohol use, as well as taking certain medications.
- Violation of metabolic processes in hepatocytes with the development of hepatosis.
- Parasitic damage to the liver.
- Traumatic damage to the liver parenchyma, as well as structures of the hepatobiliary system.
To a lesser extent, an increase in the activity of the enzymes ALT and AST can be accompanied by damage to the cells of other organs, in particular in cardiac pathology (myocardial infarction, coronary heart disease, myocarditis), thyroid (thyroiditis), pancreas (pancreatitis), lung (severe pneumonia, pulmonary infarction). Also, the activity of these enzymes can increase during hypoxia (insufficient oxygen supply to the body), as well as in shock. The main groups of reasons for the increased activity of the enzymes ALT and AST in the blood of men can be presented in the form of a table:
The group causes of increased activity of ALT and AST