Blood test for AST
What does AST blood test mean?
AST, AST, AST or aspartate aminotransferase - this is the same concept, denoting one of the enzymes of protein metabolism in the body. This enzyme is responsible for the synthesis of amino acids that make up cell membranes and tissues. Not in all organs, AST is active. Moreover, this type of aminotransferases can be attributed to specific enzymes, the excess of which indicates a fairly narrow range of pathological conditions. Most of the AST is found in the myocardium (heart muscle), hepatocytes (liver tissue), brain neurons and muscle tissue of skeletal muscles. This is due to a fairly high level of metabolic processes in them and the need for maximum fitness of cells to maintain their structure. This enzyme helps them in this.
As long as the structure of cells containing AST is not disturbed, the amount of this enzyme in plasma is minimal and does not go beyond the normal range. As soon as their integrity is violated, this leads to its excessive release into the systemic circulation. This phenomenon will be registered in the form of a natural increase in AST activity. The dependence should be directly proportional: the more active cytolysis, the higher the level of AST. The time after the onset of cell destruction is of great importance - the longer it is, the less the enzyme activity in the plasma will be.
When prescribing a biochemical blood test, they imply an analysis of the enzymatic activity of plasma, among other indicators of which ASAT is necessarily examined. This requires venous blood, which is obtained by puncture of one of the peripheral veins in the amount of 15-20 milliliters. Its centrifugation allows the plasma to be separated from the uniform elements, which then lends itself to various chemical reactions. In their course, the activity of AST in the blood is determined.
The AST study allows you to determine the presence of cell destruction (cytolysis) of the myocardium or liver. When other organs are damaged, this indicator does not increase. Very often it is prescribed not only to confirm the lesion of specific tissues, but to conduct differential diagnosis or exclude cardiac and hepatic pathology!
When is an AST test scheduled?
According to international protocols and standards for diagnosing diseases, a biochemical blood test, including an indicator of AST activity, is mandatory for many types of somatic pathology.
It can be:
- Acute and chronic diseases of the heart and circulatory system;
- Any liver pathology;
- Poisoning and intoxication;
- Kidney damage with renal failure;
- Infectious pathology;
- Purulent-septic conditions;
- Various kinds of jaundice and disorders of bilirubin metabolism;
- Signs of ascites and portal hypertension;
- Encephalopathy of unknown origin;
- Autoimmune diseases;
- Acute abdominal pathology of a surgical nature;
- Any form of gallstone disease and bile outflow disorders;
- Pancreatic necrosis and chronic pancreatitis;
- Endocrine pathology;
- Allergic skin diseases;
Malignant tumors of any localization and suspicion of their metastasis;
- Aggressive and long-term treatment with chemotherapy drugs, antibiotics and other toxic drugs;
- Preoperative preparation for any complex interventions;
- Evaluation of the dynamics and effectiveness of the treatment of liver and heart diseases;
- Injury to the chest and abdomen with suspected heart or liver contusion;
AST rate in blood
In order to correctly evaluate the obtained indicators of plasma enzymatic activity in relation to AST, you need to know its normal values. Most laboratories usually indicate the rate next to the received indicator. This is due to the fact that different reagents and methods can be used to determine the AST indicator. The types and standards given in the table are considered generally accepted.
Norm for men
Norm for women
Norm for children
Optical (in IU)
Up to 40-41 IU
Up to 34-35 IU
Up to 50 IU
Reitman-Frenkel reactions (in mmole / (h / ml))
If in the biochemical analysis of blood AST indicators are obtained that do not exceed the standard values, this indicates the normal functioning of the enzyme systems of the heart and liver and the preserved integrity of the cellular composition of these organs. In the presence of clinical symptoms of their defeat, other specific markers (ALT, troponins, creatine phosphokinase, etc.) must be investigated!
Reasons for increasing AST
Detection of an increase in the AST index, especially repeated ones, may indicate such diseases:
- Acute myocardial infarction in the initial phases of its development. The dynamics of the indicator can be judged on its vastness and recovery period;
- Closed and open heart injuries;
- Myocarditis of autoimmune or infectious origin;
- Acute and chronic viral hepatitis;
- Toxic liver damage with hepatotoxic poisons and drugs;
- Fatty and alcoholic hepatosis;
- Endogenous intoxications against the background of infectious and purulent-septic diseases of internal organs and soft tissues;
- Severe chronic heart failure;
- Cholestasis caused by a mechanical obstruction in the bile ducts (stones, tumors, congenital anomalies);
- Violation of hepatic blood flow and portal hypertension;
- Cirrhosis of the liver with the preservation of intact areas of this organ. In decompensated cirrhosis, the enzymatic activity of plasma in relation to AST decreases due to the complete replacement of the liver with connective tissue;
- Liver metastases of malignant tumors;
- Primary cancer of the liver or bile duct;
- Damage to the liver and heart in malignant forms of myeloid leukemia;
Massive destruction of muscle tissue (myodystrophy, generalized myositis, crash syndrome, reperfusion syndrome against the background of restored blood flow in the ischemic limb;
Not every increase in AST should be perceived as a sign of cellular cytolysis. If the indicator is higher than normal values by several units of measurement, this still does not mean anything. The increase in AST is two or more times higher than the norm for diagnostic purposes.
In this regard, we can talk about:
- Moderate increase (when AST rises fivefold);
- Average increase (when an increase in the indicator is recorded up to ten times higher than the norm);
- Severe increase (the AST level is ten or more times higher than the norm).
The main diagnostic value of AST is heart damage during a heart attack. The research is carried out in dynamics with short time intervals (about an hour). Any changes in the indicator exceeding the norm, in doubtful cases, speak in favor of a heart attack!
How to lower AST in the blood?
People who are looking for an answer to such a question need to clearly understand: an increase in AST is not an independent disease and therefore there are no separate measures to lower it!
Since this sign signals the destruction of cells containing this enzyme (heart, liver, muscles), it is necessary to diagnose and treat diseases of these organs. Only healthy tissues will be able to function normally and normalize all indicators of a biochemical blood test, including AST.
It should be clearly understood that an increase in AST is not the cause of the disease. This is its consequence. Therefore, only the elimination of the causative disease will be able to interrupt the causal relationship, which will be reflected in the form of normalization of AST activity and become a criterion for defeating this disease. Any cases of an increase in aspartate aminotransferase are a reason for seeking specialized medical care. This harmless and asymptomatic symptom often hides serious chronic diseases that will manifest themselves only after a while.
Article author: Mochalov Pavel Alexandrovich | d. m. n. therapist
Education: Moscow Medical Institute. IM Sechenov, specialty - "General Medicine" in 1991, in 1993 "Occupational Diseases", in 1996 "Therapy".