When referring to a biochemical blood test, the doctor notes in the form the most informative markers in terms of diagnosis. Quite often, they include liver transaminases (ALT and AST). Let’s consider what are the properties of this type of compounds and in the recognition of what diseases they can help.
Appointment in the body
According to the accepted classification, the ending “-ase” indicates that these are enzymes (the Greek-language synonym is enzymes). In total, about two thousand types of enzymes “work” in the human body. According to their function, they are divided into groups (classes).
Hepatic transaminases, which we are talking about now, have another name – aminotransferases. Both terms reflect the same essence, only the first has taken root well, and the second is more accurate in terms of nomenclature.
Transferases are called a group of enzymes involved in the “transport” of chemical groups from one type of molecule to another. Aminotransferases, as the name suggests, are involved in the transfer of amino groups. Without them, any protein-related processes would be impossible.
We are interested in two representatives of this subgroup, which, as mentioned, are of the greatest importance for clinical diagnosis:
- alanine aminotransferase (ALT, ALT),
- aspartate aminotransferase (AST, AST).
The terms alanine transaminase and aspartic transaminase mean the same. You can find spelling options: Alt and AsT, AlAt and AsAt. In everyday life they also say: alats and asats, but in general – “trances”.
Transamination reactions do occur mostly in the liver. However, having received a referral for liver tests, including transaminases, you should know that this study can be as important in recognizing heart pathology as a cardiogram made in time.
The fact is that the heart muscle, the myocardium, also needs ALT and AST. They are also contained in the pancreas, kidneys, small intestine and other organs and tissues.
Causes of deviations and their symptoms
The alats and asats perform their functions in the tissues of the organs, while in the blood their content is vanishingly small. This condition is observed in a healthy person. Everything changes when the cells affected by the disease begin to disintegrate. In this case, enzymes rush into the bloodstream, and biochemical analysis immediately notes their increase.
It is important to remember: a significant, out-of-normal, increase in hepatic transaminases indicates a progressive pathology and requires medical intervention.
First of all, liver diseases should be distinguished as the most extensive group:
- Hepatitis. This is one of the primary causes of tissue necrosis. The degree of activity of chronic forms of hepatitis and the features of its acute course determine the dynamics of changes in the level of transaminases.
- Cholestasis. Stagnation of bile ultimately leads to necrosis.
- Hypoxia (during shock).
- Fatty hepatosis (steatosis). Changes in the structure and decreased functionality of the liver parenchyma.
- Neoplasms. Both of them, as well as foci of metastases, cause inflammation and destruction of surrounding tissues.
- Parasitic invasions of the biliary system.
- The negative effects of medications. This is a number of antibiotics, NSAIDs, sulfonamides, anabolic steroids, oral contraceptives, barbiturates, immunosuppressants. Taking such drugs is dangerous for the liver, as it destroys its cells (hepatocytes).
- Genetic, hereditary diseases.
The next vital organ that may be indicated by an increase in the enzymes ALT and AST is the heart. Myocardial infarction is the death of a portion of the heart muscle, which inevitably affects biochemical processes (in this case, mainly aspartate aminotransferase increases).
Other reasons causing an increase in hepatic transaminases: acute pancreatitis, cholecystitis, sepsis, muscular dystrophy, extensive burns, skeletal muscle injuries.
The symptoms of most of these diseases are fairly well pronounced.
Liver pathologies, regardless of the variety of causes, have similar manifestations. These are dyspepsia, nausea, heaviness on the right in the hypochondrium, discoloration of urine and feces, itching, yellowness of the integument and other typical manifestations. Pain in the left side of the abdomen (especially of the girdle) may indicate acute inflammation of the pancreas, exhausting pain on the right, below the ribs, and vomiting are signs of biliary colic. Prolonged, (half an hour or more), intense pain in the heart may indicate a heart attack.
What are important in diagnostics
Transaminases increase during necrotic processes in the liver, myocardium, pancreas and other organs and tissues. Such a variety of options makes it difficult to find a real focus of pathology, does not allow to give an unambiguous answer. However, in combination with other biochemical parameters and clinical manifestations, the deviation of ALT and/or AST from the norm helps to significantly clarify the diagnostic picture.
Liver tests are especially widely used for the early diagnosis of hepatitis (A, B). An increase in the level of the enzymes ALT and AST occurs several weeks before the visible manifestation of symptoms of the disease.
Early antiviral therapy improves prognosis. (It can be added that due to the efficiency and ease of carrying out, liver tests for ALT and AST are most suitable when checking contact persons in the foci of viral hepatitis, that is, during mass examinations).
Despite the general similarity, both enzymes are concentrated in different ways in different organs, and this is also taken into account. For example, ALT is found in a greater amount in the liver, and AST in the heart, therefore, an increase in the second indicator when the first indicator lags behind indicates the development of myocardial infarction.
At the same time, this allows you to discard the suspicion of an angina attack, in which hyperenzymemia does not occur.
Another example of differential diagnosis is establishing the true cause of jaundice. With viral hepatitis, a large amount of enzymes will enter the bloodstream, which does not happen when the bile ducts are blocked.
In other cases, the task of determining the stage of the disease is solved. For example, cirrhosis is characterized by an increase in aminotransferases in the initial period, close to normal in the latent phase, and a decrease in the final period, when the cells of the hepatic parenchyma are completely destroyed and the release of enzymes has stopped.
Determination of ALT, AST levels and evaluation of results are almost never carried out in isolation from other indicators. The specificity or atypicality in the ratio of results to each other also works to narrow the range of alleged causes. An example is the so-called. bilirubin-aminotransferase dissociation: low ALT and AST values, with a pronounced increase in bilirubin. This picture is observed, for example, when the bile ducts are blocked.
The severity of hyperenzymemia is assessed according to the following conditional scale:
- 1-1,5 norms – moderate,
- 6-10 norms – average,
- 10 or more – high.
Moderate is characteristic, for example, of chronic hepatitis of viral etiology, high – is observed after a heart attack, when the norm can be exceeded fifteen or more times.
The results of ALT, AST determine further measures, the expediency of expensive examinations and hospitalization.
It should be remembered that by making a simple and accessible analysis for hepatic transaminases, or, as they say, blood biochemistry, you can save yourself from extremely severe pathologies.
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To assess the activity of manifestations of hepatic transaminases, one should start from the indicators inherent in a healthy person.
Norm for men:
- ALT – less than 45 U/l,
- AST – less than 47 U/l.
Norm for women:
- ALT – up to 34 U/l,
- AST – up to 31 U/l.
This is a very rough estimate. The fact is that there are different brands of equipment on which the analysis for liver transaminases is carried out, and the rate is calculated in different ways. Most likely, the only way to assess the result of the analysis will be to consult a specialist.
There are general patterns:
- children have the highest rates of norm, over the years the level gradually decreases and stabilizes,
- higher ALT and AST levels in men are due to the fact that the level of transaminases depends, among other things, on muscle mass.
De Ritis coefficient
When an increase in the level of hepatic transaminases exceeds the norm, their ratio becomes an additional criterion. To do this, divide the numerical indicator of AST by the numerical indicator of ALT:
k = AST/ALT
The resulting coefficient (k) is named after Fernando de Ritis, whose studies for the first time showed the relationship between this ratio and the type of pathology.
The following patterns are known:
- k ≥1 means that the cause may be chronic hepatitis or degenerative changes in the liver,
- k value <, 1 is typical for viral hepatitis,
- k = 0,55-0,83 – for acute viral hepatitis,
- k ≥2 – manifestation of alcoholic hepatitis or necrosis of the heart muscle.
In the case of the norm, that is, for ALT and AST levels in a healthy person, the de Ritis coefficient is 1,33 (+/- 0,4).
An increase in aminotransferase levels is a symptom of a disorder in the body. When the pathogenic factor is eliminated, their release into the bloodstream stops, and the indicators go down. Some diseases are completely reversible. In other cases, patient compliance with all the instructions can slow down the progress of the disease for many years.