Serum lactate dehydrogenase isoenzyme (LDHI)

Lactate dehydrogenase (LDH) in human tissues can be used to separate five isozyme bands by electrophoresis. According to their electrophoretic mobility, they are named LDH1, LDH2, LDH3, LDH4, and LDH5. The distribution of lactate dehydrogenase isoenzymes in different tissues is different, and there is obvious tissue specificity. LDH1 and LDH2 are the most in human myocardium, kidney and red blood cells, and most are LDH4 and LDH5 in skeletal muscle and liver, while lung, spleen and pancreas LDH3 is the most abundant in tissues such as thyroid, adrenal gland and lymph nodes. Later, LDHx was found in testes and sperm, and its electrophoretic mobility was between LDH4 and LDH5. LDH is composed of two subunits, H (myocardial type) and M (skeletal muscle type), forming LDH1 (H4), LDH2 (H3M), LDH3 (H2M2), LDH4 (HM3), and LDH5 (M4), respectively.

Basic Information

Specialist classification: cardiovascular examination classification: biochemical examination

Applicable gender: whether men and women apply fasting: fasting

Analysis results:

Below normal:
Serum LDH isoenzymes in healthy adults have the following regularity LDH2>LDH1>LDH3>LDH4>LDH5. Serum LDH1 and LDH2 decreased in coal mines and tungsten mines. LDH3 and LDH4 were equal in pulmonary infarction, and LDH1 was significantly decreased.

Normal value:
LDH1: 32.7-±4.6%
LDH2: 45.1-±3.5%
LDH3: 18.5-±2.7%
LDH4: 2.9-±8.6%
LDH5: 0.85-±0.55%

Above normal:
Serum LDH1 and LDH2 were significantly elevated in acute myocardial infarction. LDH1/LDH2 ratio >1 is also found in hemolytic anemia, pernicious anemia, sickle cell anemia, kidney damage, renal cortical infarction, myocardial injury disease, valvular disease and the like. Acute hepatitis was significantly elevated with LDH5, LDH4 was not increased, and LDH5/LDH4>1 was characterized. The lungs contain more LDH3, and serum LDH3 is often elevated in patients with lung disease.



Tips: Specimens avoid hemolysis. Normal value

Agarose electrophoresis LDH1 (32.7 ± 4.6)%; LDH2 (45.1 ± 3.5)%; LDH3 (18.5 ± 2.7)%; LDH4 (2.9 ± 8.6)%; LDH5 (0.85 ± 0.55)%.

Cellulose acetate film method LDH1 (24 ± 3.4)%; LDH2 (35 ± 4.4)%; LDH3 (19 ± 27)%; LDH4 (0 ± 0.05)%; LDH5 (0 ± 0.02)%.

Polyacrylamide method LDH1 (26.9 ± 0.4)%; LDH2 (36.0 ± 0.5)%; LDH3 (21.9 ± 0.4)%; LDH4 (11.1 ± 0.4)%; LDH5 (4.1 ± 0.3)%.

In conclusion, healthy adult serum LDH isoenzymes have the following regularity LDH2>LDH1>LDH3>LDH4>LDH5.

Clinical significance

The LD activity of cardiomyocytes is much higher than that of serum, especially LDH1 and LDH2. In acute myocardial infarction, serum LDH1 and LDH2 were significantly elevated. In about 95% of cases, serum LDH1 and LDH2 ratios were greater than 1, and LDH1 elevation was earlier than LDH total activity. Viral and rheumatic myocarditis and myocardial damage in Keshan disease, patients with serum LDH isoenzyme changes similar to myocardial infarction. LDH1/LDH2 ratio >1 is also found in hemolytic anemia, pernicious anemia, sickle cell anemia, kidney damage, renal cortical infarction, myocardial injury disease, valvular disease and the like.

The brain stem contains higher LDH1. When the brain damage only affects the cerebral hemisphere, only the absolute value of the serum isozyme spectrum is increased, and the ratio of the isoenzymes is not affected. If the brain stem is involved, the serum LDH1 content of the patient is also increased.

Serum LDH1 has increased 12 to 24 hours after the onset of acute myocardial infarction. If the total activity of LD is measured simultaneously, it can be found that the ratio of LDH1/total LDH is superior to the simple determination of LDH1 or CK-MB in the diagnosis of acute myocardial infarction.

Serum LDH1 activity is elevated in patients with embryonic cell tumors.

After hepatocyte injury or necrosis, a large amount of LDH4 and LDH5 are released into the bloodstream, resulting in an increase in the ratio of LDH5/LDH4 in the blood. Therefore, LDH5/LDH4>1 can be used as an indicator of hepatocyte injury. Acute hepatitis is markedly elevated by LDH5, LDH4 is not increased, and LDH5/LDH4>1 is characterized; if serum LDH5 continues to rise or fall again, it can be considered as chronic hepatitis; serum LDH5, LDH4 activity in patients with hepatic coma High, often showing poor prognosis; primary liver cancer with serum LDH4> LDH5 is more common.

The renal cortex has higher levels of LDH1 and LDH2, and the renal medulla is more active with LDH4 and LDH5. Serum LDH5 can be increased in patients with acute tubular necrosis, chronic pyelonephritis, chronic glomerulonephritis, and renal transplant rejection.

The lungs contain more LDH3, and serum LDH3 is often elevated in patients with lung disease. In the case of pulmonary infarction, LDH3 and LDH4 were equal, and LDH1 was significantly decreased. Serum LDH3 and LDH4 in patients with lung abscess were often elevated simultaneously with LDH5.

In cases with elevated serum LD activity and normal zymogram (LDH1/LDH2<1), the clinical incidence rates were cardiopulmonary disease, malignant tumor, fracture, central nervous system disorder, inflammation, cirrhosis, infectious mononuclear Cytomegaly, hypothyroidism, uremia, tissue necrosis, viremia, intestinal obstruction, etc.

LDH1 and LDH2 were significantly increased in muscles of patients with muscular dystrophy, and LDH5 was significantly decreased. In contrast, LDH1 and LDH2 were significantly decreased, and LDH4 and LDH5 were significantly increased, indicating that serum LDH isoenzymes were mainly derived from muscle tissue. In the coal mines and tungsten mines, the serum levels of LDH1 and LDH2 decreased, and LDH4 and LDH5 increased.

Low results may be diseases: high myocardial infarction results may be diseases: neonatal myocarditis, hemolytic anemia considerations

First, the precautions before blood draw

1, do not eat too greasy, high-protein food the day before the blood, to avoid heavy drinking. The alcohol content in the blood directly affects the test results.

2. After 8 pm on the day before the medical examination, you should start fasting for 12 hours to avoid affecting the test results.

3, should relax when taking blood, to avoid the contraction of blood vessels caused by fear, increase the difficulty of blood collection.

Second, should pay attention after blood draw

1. After blood is drawn, local compression is required at the pinhole for 3-5 minutes to stop bleeding. Note: Do not rub, so as not to cause subcutaneous hematoma.

2, the pressing time should be sufficient. There is a difference in clotting time for each person, and some people need a little longer to clotting. Therefore, when the surface of the skin appears to be bleeding, the compression is stopped immediately, and the blood may be infiltrated into the skin due to incomplete hemostasis. Therefore, the compression time is longer to completely stop bleeding. If there is a tendency to bleed, the compression time should be extended.

3, after the blood draw symptoms of fainting such as: dizziness, vertigo, fatigue, etc. should immediately lie down, drink a small amount of syrup, and then undergo a physical examination after the symptoms are relieved.

4. If there is localized congestion, use a warm towel after 24 hours to promote absorption.

Third, the specimen avoids hemolysis.

Serum (serum should be separated from blood clot as soon as possible), store at room temperature for up to 3 days; LDH5 is the most unstable (all inactivation at 50 °C, 13% inactivation at 48h at normal temperature, 18% at 48°C for 48h; LDH4 at -25°C overnight) All LDH5 is inactivated; specimens are strictly prohibited from hemolysis; the substrate coloring solution is now available and should be placed away from light.

Inspection process

Take an appropriate amount of blood, immediately sent to the test, agarose electrophoresis detection.

Not suitable for the crowd

Inappropriate people: Generally there are no people who are not suitable.

Adverse reactions and risks

1. Infection: Pay attention to aseptic operation when collecting blood, avoid contamination of water and other parts at the blood collection site to avoid local infection.
2, bleeding: after the blood is given a full compression time, especially coagulopathy, bleeding tendency, to avoid local subcutaneous oozing, bruising and swelling.