How long does it take to test for LDH? Lactate dehydrogenase (LDH) in the blood: what is it, the norm in the analysis, reasons for the increase. When is this test prescribed?

LDH (L-lactate-NAD-oxidoreductase, EC 1.1.1.27) is a zinc-containing enzyme that reversibly catalyzes the oxidation of lactate to pyruvate. LDH is a tetramer, contains subunits M and H. In the cytoplasm of cells and blood serum, LDH is represented by 5 isoenzymes, designated according to their mobility to the anode in the electric field: LDH-1 (NNNN), LDH-2 (NNNM), LDH-3 (NNMM), LDG-4 (NMMM) and LDG-5 (MMMM). LDH is present in almost all organs and tissues of the body, and the distribution of LDH isoenzymes is organ specific. LDH-4 and LDH-5 predominate in the liver and skeletal muscles, tissues with predominantly anaerobic metabolism, LDH-1 and LDH-2 - erythrocytes, leukocytes, myocardium, kidneys - tissues with aerobic metabolism, the highest content of LDH-3 is in lungs, lymphoid tissue, platelets and tumors.

MI is usually accompanied by a 3–4-fold increase in total LDH activity; A similar increase in LDH is observed in myocarditis and cardiac arrhythmias. During MI, an increase in total LDH activity in the blood serum is observed after 8–10 hours, and reaches maximum activity after 48–72 hours. The release of myocardial LDH isoenzymes into the blood during MI leads to an increase in the activity of LDH-1 and LDH-2. LDH-1 activity increases 12–24 hours after the onset of acute MI, coinciding in time with the maximum of CK-MB activity and ahead of the peak of total LDH activity (24 hours).

Identification of the spectrum of isoenzymes characteristic of MI is possible with blood stagnation in the liver and kidneys due to heart failure, with ischemic damage to some organs due to a sharp decrease in cardiac output. Currently, determination of the activity of LDH and its isoenzymes is not among the mandatory tests for diagnosing MI due to insufficient specificity.

Myopathies, liver diseases, megaloblastic and hemolytic anemias, acute and chronic kidney diseases lead to increased LDH activity. An increase in LDH activity is observed with liver damage, but this increase is not as great as the increase in ALT and AST activity. A particular increase (10 times higher than the upper limit of normal) is noted in toxic hepatitis accompanied by jaundice.

A physiological increase in LDH levels in the blood occurs during pregnancy, in newborns, and also after intense physical activity.

Indications for the study:

Liver diseases;
detection of myocardial lesions;
myopathies;
hemolytic anemia;

Serum or plasma (EDTA, heparin) without signs of hemolysis. Store samples for no more than 2 days at 18–25°C. Storing samples at 4–8°C or freezing reduces enzyme activity.

Research methods. Method based on IFCC recommendations. LDH catalyzes the oxidation of lactate to pyruvate at alkaline pH, while NAD+ is reduced to NADH. The rate of increase in the optical density of the reaction mixture at 340 nm, reflecting an increase in the concentration of NADH, is proportional to the enzyme activity in the sample.

Increased values:

Myocardial damage;
liver damage;
damage, inflammatory and degenerative diseases of skeletal muscles;
embolism and pulmonary infarction;
kidney diseases;
diseases and conditions accompanied by cell breakdown;
malignant tumors of any location;
taking anabolic steroids, ethanol, hepatotoxic drugs.

Reduced values:

Isoenzymes LDH-1 and LDH-2

LDH-1 and LDH-2 are isoenzymes with a high content of H-subunits that can use α-ketobutyrate as a substrate and catalyze its conversion to α-hydroxybutyrate; the LDH-1 isoenzyme, which has a high affinity for the named substrate, is called α-hydroxybutyrate dehydrogenase (α-HBDH). A parallel study of the activity of total LDH and α-HBDG can be used for the differential diagnosis of diseases of the liver and heart: with damage to the heart muscle, an increase in enzyme activity is due to an increase in LDH-1 (α-HBDG), with damage to the liver parenchyma - by the LDH-5 isoform, LDH activity -1 does not increase.

Indications for the study:

Detection of myocardial lesions;
hemolytic anemia;
malignant neoplasms;
pulmonary embolism (differential diagnosis with myocardial infarction).

Features of sampling and storage. Serum or plasma (EDTA, heparin) without signs of hemolysis. Store samples for no more than 2 days at 18–25°C. Storing samples at 4–8°C or freezing reduces enzyme activity.

Research methods. LDH catalyzes the conversion of α-ketobutyrate to α-hydroxybutyrate, which results in the oxidation of β-NADH2 to β-NAD. The rate of decrease in optical density at a wavelength of 340 nm is proportional to the enzyme activity in the sample.

Increased values:

Myocardial damage;
diseases and conditions accompanied by the breakdown of blood cells;
acute kidney diseases.

Reduced values:

Genetic disorders or complete absence of LDH subunits.

LDH blood test is lactate dehydrogenase (LDH)- an enzyme contained in the cells of the heart muscle, liver, kidneys, lungs, and skeletal muscles. In this regard, in clinical practice, separate isoenzymes are distinguished: LDH1 and LDH2 (found mainly in the myocardium and kidneys), LDH3 (found mainly in the lung tissue), LDH4 and LDH5 (found in the largest quantities in the liver and skeletal muscles), the information content of which higher than when determining total LDH.

Promotion LDH (especially LDH1 and LDH2) is most often observed in acute myocardial infarction, while in angina (including unstable) this indicator remains normal, which allows its use along with creatine kinase (for details, see the position “creatine kinase” and “creatine kinase MV ") for the differential diagnosis of these conditions with a questionable ECG picture. A moderate increase in LDH is also observed in patients with acute myocarditis, severe heart failure with congestion in the liver, as well as with the development of pulmonary embolism. A significant increase in both total LDH and its isoenzymes LDH4 and LDH5 is observed in acute hepatitis, liver cirrhosis in the acute stage, as well as in cancer of the liver. LDH activity also increases with mechanical jaundice (most often when the bile ducts are blocked by a stone or compressed by a tumor) and hemolytic anemia. A moderate increase in this indicator is possible with extensive traumatic muscle injuries and with progressive muscular dystrophy.

Decline LDH activity is not important in clinical practice.

Biological material: blood serum

In diseases accompanied by tissue damage and cell destruction, LDH activity in the blood increases. In this regard, it is an important marker of tissue destruction. Despite the fact that an increase in enzyme activity does not indicate a specific disease, its determination in combination with other laboratory tests helps in the diagnosis of pulmonary infarction, muscular dystrophy and hemolytic anemia. Increased LDH activity can be detected in newborns, pregnant women and after intense physical exercise.

Previously, combined tests for LDH, aspartate aminotransferase and creatine kinase were widely used in the diagnosis of myocardial infarction. Now, for this purpose, the level of troponin is determined as a more specific marker of damage to the heart muscle. But the study of LDH activity remains an auxiliary analysis in the differential diagnosis of chest pain.

Monitoring the course of myocardial infarction. An increase in LDH activity is observed 12–24 hours after a heart attack; maximum activity is observed after 24 - 48 hours. Increased enzyme activity lasts up to 10 days. LDH activity depends on the size of the myocardial lesion, and the dynamics of its decrease during the recovery process depends on the intensity of recovery processes in the heart muscle.

Determination of LDH activity makes it possible to differentiate between true myocardial infarction and clinically similar attacks of angina: during a heart attack, the total activity of LDH increases and, as a result, its value is several times higher than the normal level, while at the same time, even with severe attacks of angina, the level of LDH activity is normal. The decrease in enzyme activity in the post-infarction period occurs 2 times slower than the normalization of such markers of myocardial damage as creatine kinase and AST, which is especially valuable for late diagnosis of damage.

Indications for the purpose of the study

1. Diseases of the hepatobiliary system;
2. Myocardial infarction (early diagnosis, differential diagnosis and monitoring);
3. Tumors;
4. Anemia accompanied by hemolysis.

Preparing for the study

GENERAL RULES FOR PREPARATION FOR RESEARCH:

1. For most studies, it is recommended to donate blood in the morning, from 8 to 11 o’clock, on an empty stomach (at least 8 hours must pass between the last meal and blood collection, you can drink water as usual), on the eve of the study, a light dinner with a restriction eating fatty foods. For tests for infections and emergency studies, it is acceptable to donate blood 4-6 hours after the last meal.

2. ATTENTION! Special preparation rules for a number of tests: strictly on an empty stomach, after a 12-14 hour fast, you should donate blood for gastrin-17, lipid profile (total cholesterol, HDL cholesterol, LDL cholesterol, VLDL cholesterol, triglycerides, lipoprotein (a), apolipo-protene A1, apolipoprotein B); The glucose tolerance test is performed in the morning on an empty stomach after 12-16 hours of fasting.

3. On the eve of the study (within 24 hours), avoid alcohol, intense physical activity, and taking medications (in consultation with your doctor).

4. 1-2 hours before donating blood, refrain from smoking, do not drink juice, tea, coffee, you can drink still water. Avoid physical stress (running, quickly climbing stairs), emotional excitement. It is recommended to rest and calm down 15 minutes before donating blood.

5. You should not donate blood for laboratory testing immediately after physiotherapeutic procedures, instrumental examination, X-ray and ultrasound examinations, massage and other medical procedures.

6. When monitoring laboratory parameters over time, it is recommended to conduct repeated tests under the same conditions - in the same laboratory, donate blood at the same time of day, etc.

7. Blood for research must be donated before starting to take medications or no earlier than 10–14 days after they are discontinued. To assess the control of the effectiveness of treatment with any drugs, a study should be conducted 7-14 days after the last dose of the drug.

If you are taking medications, be sure to notify your doctor.

The glycolytic intracellular (cytoplasmic) enzyme lactate dehydrogenase (LDH), which accelerates the reaction of converting lactic acid into pyruvic acid, and also catalyzes the reverse reaction (the reversible oxidation reaction of L-lactate to pyruvate), is present without exception in all tissues of the human body. The highest content of LDH is observed in the heart, liver and kidney parenchyma, skeletal muscles, red blood cells, where the enzyme is presented in the form of five isoenzymes (isoenzymes): LDH-1, LDH-2, LDH-3, LDH-4, LDH-5. The electrical mobility of these isoenzymes fully corresponds to that of globulins - α 1, β 1, γ 1, γ 2. The main concentration of LDH is concentrated inside the cells; serum is noticeably inferior in this regard.

In an adult who does not complain about his health, The total activity of lactate dehydrogenase in blood serum normally ranges from 0.80 to 4.00 mmol/(h l) or 38 – 62 U/l ( at 30°C).

Distribution of fractions in plasma. Age and norm

The first fraction (LDH-1 or HHNN tetramer) originates primarily in the cardiac muscle and is significantly increased in the blood serum with myocardial damage.

The second, third, fourth fractions (LDG-2, LDH-3, LDH-4) begin to actively enter the plasma under pathological conditions accompanied by massive death of blood platelets - platelets, which occurs, for example, in the case of such a life-threatening condition as pulmonary embolism (PE).

The fifth isoenzyme (LDH-5 or MMMM tetramer) comes from the cells of the liver parenchyma and is released into the blood plasma in large quantities at the acute stage of viral hepatitis.

Due to the fact that different types of tissue accumulate and release different concentrations of LDH, fractions of lactate dehydrogenase isoenzymes are distributed unevenly in the blood plasma:

Isoenzyme	Serum concentration
LDH-1	17 – 27% (0.17 – 0.27 relative units)
LDG-2	27 – 37% (0,27 – 0,37)
LDG-3	18 – 25% (0,18 – 0,25)
LDG-4	3 – 8% (0,03 – 0,08)
LDG-5	0 – 5% (0,00 – 0,05)

The activity of lactate dehydrogenase in red blood cells (erythrocytes) is 100 times higher than the levels of the enzyme contained in the blood plasma, and increased values are observed not only in pathological conditions, but also in a number of physiological conditions, for example, pregnancy, the first months of life or excessive physical effort on their part also contribute to an increase in LDH activity. Significant differences in the normal levels of this indicator are also due to age and gender, as evidenced by the table below:

Meanwhile, the normal values for blood LDH are always approximate; they should not be memorized once and for all for the reason that the analysis can be performed at a temperature of 30°C or 37°C, the level is calculated in different units (μkat/l, mmol/( h·l), U/l or U/l). But if there is an urgent need to independently compare your own results with the normal variants, then it will be useful to first inquire about the institution that performed the analysis, the methods of its implementation and the units of measurement used by this laboratory.

Excretion of lactate dehydrogenase isoenzymes (LDH-4, LDH-5) by the kidneys does not exceed the level of 35 mg/day (excretion rate).

Reasons for increased LDH

The level of LDH activity is increased in almost any pathological process that is accompanied by inflammation and death of cellular structures, therefore the reasons for the increase in this indicator are primarily considered to be:

Acute phase (a more detailed description of changes in the LDH spectrum during necrotic myocardial damage will be presented below);
Functional failure of the cardiac and vascular system, as well as the respiratory system (lungs). Involvement of lung tissue in the process and the development of circulatory failure in the pulmonary circulation (LDH levels are increased due to the activity of LDH-3 and, to some extent, due to LDH-4 and LDH-5). Weakening of cardiac activity leads to circulatory disorders, symptoms and an increase in the activity of fractions LDH-4 and LDH-5;
Damage to red blood cells (pernicious and), causing a state of tissue hypoxia;
Inflammatory processes affecting the lungs, as well as the renal or hepatic parenchyma;
Acute period of viral hepatitis (in the chronic stage, LDH activity, as a rule, does not leave the normal range);
Malignant tumors (especially those with metastasis), localized mainly in the liver tissue. Meanwhile, a strict correlation, in contrast to myocardial infarction (the larger the size of the lesion, the higher the activity of LDH) between the progression of the oncological process and changes in the spectrum of lactate dehydrogenase is not traced;
Various hematological pathologies (acute, granulocytosis, chronic myeloblastic leukemia, or folic acid deficiency);
Massive destruction of platelets, which is often caused by platelets that are not provided with sufficient selection for individual blood systems (for example, HLA);
Diseases of the musculoskeletal system, primarily damage to skeletal muscles (injuries, atrophic lesions, mainly at the initial stage of disease development).

LDH and cardiac muscle necrosis

The study of the glycolytic enzyme is of very important diagnostic value in case of damage to the heart muscle, therefore refers to the main enzymatic tests that determine myocardial infarction on the first day development of a dangerous necrotic process localized in the heart muscle (8–12 hours from the onset of pain). The increase in enzyme activity occurs, first of all, due to the LDH-1 fraction and partly due to the second fraction (LDH-2).

After a day or two from a painful attack, the level of LDH in the blood reaches its maximum values and in most cases remains highly active for up to 10 days. It should be noted that activity is directly dependent on the area of myocardial damage(the larger the size of the lesion, the higher the indicator values). Thus, myocardial infarction, initially diagnosed using laboratory tests such as determination of creatine kinase and the MB fraction of creatine kinase, can be confirmed within a day by this enzymatic test (LDG is elevated and increased significantly - 3 - 4 ... up to 10 times).

In addition to increasing the total activity of lactate dehydrogenase and increasing the activity of the LDH-1 fraction, the LDH/LDH-1 or HBDG (hydroxybutyrate dehydrogenase) ratio and the LDH-1/LDH-2 ratio are of particular value for detecting acute myocardial infarction. Considering that the GBDG values in the acute period of the disease change significantly upward, and the total activity of lactate dehydrogenase will be reduced relative to the rather high LDH-1 values, the LDH/GBDG ratio will noticeably drop and will be below 1.30. At the same time, the LDH-1/LDG-2 ratio, on the contrary, will tend to increase, tending to reach 1.00 (and sometimes even cross this line).

Other reasons for changing odds

The above parameters, in addition to necrotic damage to the heart muscle, are also subject to changes in the case of other serious diseases:

Hemolytic anemia of various origins (LDG/GBDG decreases and becomes below 1.3);
Megaloblastic anemia (the content of the first fraction significantly exceeds the concentration of the second);
Conditions accompanied by increased cell destruction (acute necrotic process);
Neoplasms localized in the glands of the female and male reproductive system: ovarian dysgerminoma, testicular seminoma, teratoma (here only an increase in the concentration of LDH-1 is noted);
Renal parenchyma lesions.

Thus, the main culprits, and therefore the main reasons for changes in the concentration of the described indicators in the blood serum, can be considered conditions associated with the destruction of liver and kidney parenchyma cells, as well as blood cells (platelets, erythrocytes).

Some nuances

To study LDH in the blood, 1 ml of serum is sufficient, which is obtained from blood donated, as for any other biochemical test, in the morning on an empty stomach (however, if there is a question about diagnosing acute MI, then these rules, of course, are neglected).

In a laboratory study of LDH, hemolysis leads to distortion of the analysis results (overestimates them). And when exposed to heparin and oxalate, the enzyme activity in the serum, on the contrary, will be reduced compared to the real blood LDH values. To prevent this from happening, you should start working with the material as early as possible, first of all separating the clot with formed elements from the serum.

Video: specialist about LDH

An LDH (lactate dehydrogenase) test is a test for the level of an enzyme in the blood that oxidizes glucose and is responsible for the synthesis of lactic acid.

This indicator is nonspecific and does not correspond to certain diseases and pathologies, since this enzyme is found in almost all tissues and cells of the body.LDH analysis is an important indicator of the destruction of cells and tissues in the body. It is included in the list of mandatory indicators.

Lactate dehydrogenase is a special enzyme found in most cells of the body. Greater activity of this enzyme is observed in muscle tissue, and.

LDH analysis is a nonspecific indicator of tissue destruction in the body. When the LDH indicator is assessed only in conjunction with other blood parameters.

The enzyme is present in the body in the form of five isoforms, differing not only in composition, but also in the place of concentration in the body. For example, LDH in isoform 1 is concentrated in the heart muscle. When cardiac tissue cells are destroyed, LDH-1 is released into the blood and its concentration increases. This indicator is used for early diagnosis of myocardial infarction.

LDH isoform 5 is concentrated in liver tissue and muscle, and LDH isoform 3 is concentrated in lung tissue. Together with other, more specific blood indicators, LDH is used as a marker of various pathological processes in the body.

Depending on which LDH isoform predominates in the tissue, the type of breakdown depends: aerobic or anaerobic.

LDH analysis is mandatory when taking a biochemical blood test. It is prescribed for almost any and for preventive purposes.

More information about the LDH enzyme can be found in the video:

Particular attention is paid to the lactate dehydrogenase indicator in the following cases:

If you suspect . With anemia, they are destroyed faster and the level of LDH contained in blood cells increases. An LDH test is prescribed for symptoms of anemia, for example, pale skin, chronic fatigue, dizziness, and tinnitus.
For monitoring, diagnosing and checking the effectiveness of treatment of myocardial infarction. When the heart muscle is destroyed, the level of LDH increases significantly.
If you suspect a tumor disease. With cancer, many cells in the body begin to break down, releasing an enzyme into the blood.

Preparation and procedure

To find out your LDH level, you need to donate blood from a vein. The procedure itself is standard: the patient comes with a coupon to the laboratory at the appointed time and donates blood from a vein. In paid laboratories you can donate blood without a coupon or registration.

Since LDH is a nonspecific indicator, special preparation for the procedure is not required. When testing, it is used. To make it suitable for analysis, it is advisable to carry out standard, simple preparation.

The reliability of the test results depends not only on the laboratory technicians and compliance with the rules of blood sampling, but also on the patient himself.

Blood from a vein is donated in the morning, preferably before 10 am. You do not need to follow any special diet, but you should not eat anything in the morning before the test, otherwise the blood will clot and become unsuitable for analysis. The last meal should be 6-8 hours before visiting the laboratory.
Despite the absence of a diet, it is undesirable to overeat and consume large amounts of fatty and protein foods the day before the test. Increased levels of fat and protein in the blood cause the blood serum to become cloudy, causing it to clot, making it impossible to perform a test.
It is not recommended to drink alcohol the day before donating blood. It will negatively affect the condition of the body, which will invariably affect blood counts. Results may not be reliable.
Smoking also has a negative effect on the blood. It is not advisable to smoke on the day of the examination or at least an hour before donating blood.
It is not recommended to take any medications on the day of donating blood. All medications taken should be reported to your doctor. Aspirin, oral contraceptives and strong antidepressants can affect blood clotting and distort indicators.
Physical activity can also affect the test result. The day before visiting the laboratory and on the day of donating blood, it is not advisable to engage in intense sports.

Explanation: norm and reasons for lowering the indicator

Only a doctor should interpret the results. It is impossible to talk about any diseases based on LDH alone. To get a complete picture, you need to evaluate all blood parameters.

LDH levels may vary depending on the age or condition of the patient. For example, for athletes and pregnant women, the normal level of LDH is slightly higher than for others.

Normal LDH levels in the blood:

In the blood of newborn infants, the level of LHD is always elevated. The norm is considered to be from 220 to 600 units/l.
In children after one year, this figure decreases to 115-300 units/l.
For women and men, the norm is practically no different. The lower limit is the same for everyone: 125 units/l, and the upper limit for women is 210 units/l, for men – 225 units/l.

A low level of LDH (below 125 U/L in an adult) is very rare and is almost never considered as an indicator of a pathological condition of the body.

A reduced enzyme level indicates that glucose is being broken down very actively in the body.

Among the reasons for a decrease in the level of lactate dehydrogenase in the blood are the following:

A large amount of vitamin C. If a person actively consumes ascorbic acid or products containing it, the level of LDH in the blood decreases.
Taking medications that reduce the amount of enzyme in the blood. Such drugs include Amikacin, Naltrexone, Enalapril, Metronidazole, Cefotaxime.
The presence of oxalates and urea in the blood, which neutralize LDH. Typically, similar phenomena are observed with stones in the kidneys, bladder, and urinary ducts.

Reasons for the increase

The reasons for the increase in blood levels can be both physiological (physical activity, newborn age) and pathological.

It is impossible to determine the disease only by the level of LDH, since this is a nonspecific indicator; it only indicates the presence of destructive processes in the tissues of the body.

Reasons for increased LDH:

Myocardial infarction. During myocardial infarction, muscle tissue suffers. It breaks down, releasing various enzymes into the blood, one of which is LDH. helps to detect myocardial infarction even before symptoms appear. LDH in the blood increases within 24 hours after the onset of the disease, after 4 hours, after 4-8 hours.
. Anemia is accompanied by a reduced level, which, when destroyed, releases LDH. With anemia, there is usually a decreased level of iron in the blood and an increased level of LDH. most common. It is often caused by poor nutrition and is regulated by.
Leukemia. With leukemia (an oncological blood disease accompanied by abnormal, pathological production of blood cells), the activity of many enzymes increases: , LDH, the level of and. The content of glucose and fibrinogen, on the contrary, decreases.
Malignant tumors. Most often, oncology is diagnosed using. With the help of biochemistry, one can only suspect a malignant tumor. Oncological disease is often accompanied by elevated levels of AST and LDH. Tumor processes affect many tissues and organs, so many blood parameters may change.
Acute pancreatitis. An attack of acute pancreatitis is accompanied by severe pain and often requires hospitalization of the patient. In case of pancreatitis, first of all, attention is paid to the level of (pancreatic enzyme). The level of bilirubin and LDH may also increase.

Normalization of LDH levels in the blood

To normalize the level of LDH in the blood, you need to correctly determine the reason for its increase, taking into account other blood parameters. Only eliminating the disease that causes an increase in LDH in the blood will give results.

Features of the treatment of pathology:

Treatment of myocardial infarction begins at the first symptoms of the disease or immediately after a heart attack is detected. The patient's load on the heart is reduced, fresh air is provided, and medications are administered to normalize blood circulation and maintain heart function. During treatment, the patient constantly donates blood so that the doctor can monitor the effectiveness of the treatment. With sufficiently effective treatment, the level of LDH and other indicators will decrease.
If an increase in LDH levels is caused by iron deficiency anemia, iron supplements containing foods rich in iron, ascorbic acid are prescribed, and walks in the fresh air are recommended. During treatment, blood is donated to monitor effectiveness. If treatment is effective and the cause of anemia is eliminated, LDH levels will fall and rise.
Treatment of malignant tumors is carried out comprehensively using various aggressive methods of influencing cancer cells, for example, chemotherapy, radiation therapy. Not long ago, a drug was invented that blocks the production of LDH in the cells themselves, which makes it possible to reduce tumor growth and even get rid of it completely. Such treatment is effective in the initial stages. In the absence of metastases, surgery is prescribed to remove the tumor (to replace bone marrow for leukemia).
Treatment of acute pancreatitis is most often carried out in a hospital setting, the level of LDH in the blood is constantly monitored. The patient is prescribed painkillers, digestive enzymes, plasma drips, etc. If drug therapy does not produce results, the patient is prescribed rinsing and, in extremely rare cases, removal surgery.

The LDH (lactate dehydrogenase) test is a nonspecific test that is used when a number of diseases and conditions are suspected. The enzyme enters the blood plasma during the destruction of almost any cell in the body, including bacterial ones. Therefore, the level of LDH in the blood is a general indicator of tissue and cellular damage. Sometimes the concentration of a substance is assessed using cerebrospinal or pulmonary fluid in the presence of certain diseases.

The importance of the enzyme in the body

Interest in what LDH is in a biochemical blood test is associated primarily with myocardial infarction. Previously, this test was used to diagnose and monitor damage to cardiac tissue, but now the troponin test is considered more accurate and informative. Lactate dehydrogenase (LDH) is not a specific indicator of cardiac cell damage and is no longer used in patients with suspected acute coronary syndrome. Typically, the transcript of a biochemical blood test contains this indicator. Lactate dehydrogenase in the blood is an important enzyme involved in the reactions:

Glucose oxidation;

Lactic acid production.

The peculiarity of the enzyme is that it does not accumulate in cells, but is completely broken down and excreted. LDH is essential for converting glucose into energy for the functioning of all cells in the body. The reaction is mediated by oxygen, which helps break down glucose into water, carbon dioxide and energy. Without oxygen, energy production decreases by 20 times and lactic acid accumulates. The enzyme LDH is necessary for its oxidation and return to glucose metabolism. Unlike healthy cells, cancerous tumors feed without oxygen.

When is the test prescribed?

The test is used when acute and chronic tissue damage is suspected, as well as to evaluate progressive diseases. In rare cases, the test can help identify target organ damage.

The enzyme is determined in a venous blood sample. After injury, LDH is elevated, rises for 48 hours and reaches a maximum after 2-3 days, then gradually decreases. The normal level is restored within 10 days.

Research shows that the LDH blood chemistry test is an indicator of cancer development and progression. Even after taking into account the factor of age and stage of the disease in patients, a strong association with the risk of death remained. This relationship was true for all types of malignant tumors.

The blood LDH test can be used to detect and evaluate:

Acute or chronic tissue damage;

Progression of anemia and severe infection;

Courses of cancer after chemotherapy, leukemia, melanoma, neuroblastoma. High values indicate poor prognosis for patient survival.

The doctor prescribes determination of LDH levels in other body fluids:

To distinguish between bacterial and viral meningitis by analyzing cerebrospinal fluid.

To identify the cause of the accumulation of fluid in the chest or abdomen (pleural, peritoneal and pericardial fluids) due to trauma and inflammation or due to an imbalance of pressure within the blood vessels and the amount of protein in the blood.

A blood test for LDH (biochemistry) is taken on an empty stomach from a vein.

The last meal 8 hours before the examination should not contain too much fatty or protein foods.

Be sure to inform if you need to take medications regularly. Aspirin, hormonal contraceptives and antidepressants affect clotting and may show elevated values.

Intense training the day before can lead to an increase in the enzyme, as it increases energy expenditure and the need for the breakdown of glucose.

Many factors influence the results of the analysis, and they are not always a cause for concern and further examination:

Blood samples produce false positive results. Violation of the rules for storing samples and rough processing affect the accuracy.

With increased platelet count, serum LDH level also increases and does not show the real picture.

During hospitalization with suspected myocardial infarction and acute pancreatitis, LDH analysis is performed without taking into account the recommendations. Often, the LDH indicator is used to assess the dynamics of the disease and the patient’s recovery.

Norm of LDH in the body and interpretation of the analysis

When testing blood, the norm is usually indicated in units/l, which means one per liter. The interpretation of the analysis takes into account the age and gender of the patient. A relatively small amount of the enzyme is found in the blood of a healthy adult. In a child under two years of age, the norm is considered to be within 430 units/l.

An increase in lactate dehydrogenase occurs during pregnancy, in newborns, and in professional athletes.

Based on the identified marker, it is impossible to determine which cells were damaged. Therefore, when deciphering LDH, it is necessary to know what its isoenzymes are. Some laboratories conduct additional tests that determine several forms of the substance, starting with the most mobile:

The first indicates a problem with the heart, kidneys and red blood cells;

The second is found mainly in cardiomyocytes and erythrocytes;

The third is found in lung tissue, endocrine glands and adrenal glands;

the fourth is an enzyme in white blood cells, liver, placenta and male testicles and muscle tissue;

The fifth is found in all organs containing LDH-4, as well as skeletal muscles.

Deciphering biochemistry for increased LDH in the blood is now considered less informative.

High values of all isoenzymes determine the pathology of several organs. Myocardial infarction with congestive heart failure causes lung damage and liver congestion. In cancer and autoimmune diseases such as lupus, lactate dehydrogenase is generally elevated. Hypoxia, shock and burns are accompanied by cell death, which shows an increase in LDH. Caffeine also affects the amount of enzyme in the blood.

The dynamics of the first isoenzyme are more sensitive and specific than the increase in LDH in general. Usually the level of the second isoenzyme is higher than the first. If the concentration of LDH-1 increases relative to LDH-2, a heart attack is diagnosed. Typically, the LDH level in the blood is exceeded 12-24 hours after damage to heart tissue and for two days in 80% of cases. A normal LDH-1/LDH-2 ratio is reliable evidence that there was no attack. The ratio of total LDH to LDH-1 is called hydroxybutyrate dehydrogenase. Therefore, during a heart attack:

The LDH/GBDG figure is reduced (less than 1.30);

The LDH-1/LDG-2 ratio approaches 1 and sometimes exceeds this value.

On the first day, myocardial infarction is diagnosed by the creatine kinase indicator, and a day later - by the enzymatic study of LDH. The activity of the substance is directly related to the area of damage to the heart muscle.

Other serious diseases are reflected in the ratio of isoenzymes and coefficients:

Hemolytic anemia is characterized by a low LDH/GBDG figure - up to 1.3 and below;

In megaloblastic anemia, LDH-1 significantly exceeds LDH-2;

the general level increases during acute necrotic processes and cell death, such as damage to the kidney parenchyma;

tumors in the gonads (ovaries and testes) are accompanied by an isolated increase in LDH-1.

Most often, LDH is elevated due to the destruction of tissue of the liver and kidney parenchyma, and the death of platelets and red blood cells.

LDH in a blood test is considered in relation to other indicators:

With anemia, red blood cells are destroyed, which releases large amounts of LDH into the blood. The disease is diagnosed against the background of low hemoglobin. Weakness, pallor, shortness of breath may be indications for examination.

Blood cancer is associated with the production of abnormal blood cells, which is reflected in the levels of many indicators: LDH, aspartate aminotransferase, bilirubin, urea. At the same time, there is a decrease in the level of glucose and the blood clotting factor fibrinogen. A biochemical blood test allows one to suspect pathology and refer the patient to identify tumor markers.

Along with the LDH level in the blood, which indicates the death of pancreatic cells, bilirubin and glucose will increase. The primary indicator is the level of the pancreatic enzyme amylase.

Reasons for the increase

Elevated LDH levels can be caused by various diseases:

stroke;
some types of anemia (pernicious and hemolytic)
kidney and liver diseases;
muscular dystrophy;
pancreatitis;
Infectious mononucleosis;
some forms of cancer.

The concentration of the enzyme increases after the administration of anesthetics and aspirin, as well as after intense physical exercise. Normal and decreased LDH levels are not pathological. A factor that reduces the indicator is the consumption of a large dose of ascorbic acid (vitamin C).

The reasons that lactate dehydrogenase is elevated are varied: HIV infection, sepsis, acute kidney disease, infarction of the intestines and lungs, bone fractures, rash on the body.

LDH is low when transudate accumulates in body cavities, such as the abdomen, usually caused by congestive heart failure or cirrhosis.