- LDH can be done on serum or plasma.
- Can store the sample at room temperature.
- Perform the test immediately.
- The hemolyzed sample is not acceptable because RBC has LDH.
- LDH can be done on urine and CSF.
- The serum is preferred to plasma.
- The plasma may not be used due to the presence of platelets which has a high quantity of LDH.
- Separate the serum as soon as possible, immediately after the clot formation.
- Do not refrigerate or freeze and perform the test immediately.
- The hemolyzed serum has 150 times more LDH due to the RBCs, particularly LDH-1 and LDH-2 than the clear serum.
Purpose of the test (Indication)
- LDH used to diagnose the diseases or injury to:
- Heart muscles.
- Skeletal muscles.
Nonspecific tumor marker.
- Helpful in the diagnosis of exudative fluid near the malignant tumors.
- LDH-2 is high in 35% of the cases.
- Hemolysis raises the LDH level like myocardial infarction.
- There is raised the level of LDH 1 and 2 in megaloblastic anemia.
- LDH is an enzyme present in all the body cells and presents only in the cytoplasm of cells.
- LDH is present in the heart, liver, RBCs, kidney, skeletal muscles, lung and brain.
- Its molecular weight is 134,000.
- It consists of four peptides chains of two types, M (or A) and H (orB).
- This M is for muscles and H is for the heart.
- LDH-1 = HHHH (H4).
- LDH-2 = HHHM (H3M).
- LDH-3 = HHMM (H2M2).
- LDH-4 = HMMM (HM3).
- LDH-5 = MMMM (M4)
- These are controlled by the loci on human chromosomes no 11 and 12 respectively.
- Five isoenzymes make the total LDH. These are separated by electrophoresis (Thin layer agarose gel) and These are:
- LDH 1 is present in the cardiac muscle, RBCs, and kidney cortex.
- LDH 2 is present in the cardiac muscle and RBCs.
- LDH 3 is present mainly in the lung and other tissues.
- LDH 4 is present in the kidneys, pancreas, and placenta.
- LDH 5 is present in the skeletal muscles and liver.
- LDH enzyme level in U/g in various tissue is high as compared to the serum e.g:
- Skeletal muscles = 147
- liver = 145
- Heart = 124
- Kidney = 106
- RBC (U/g Hb) = 36
- Tissue level of LDH is roughly 500 times more than the serum. So contamination with damaged tissue will give very high values.
- LDH is an enzyme of the oxidoreductase class that catalyzes the reduction of pyruvate to L-lactate.
- LDH enzyme catalyzes the oxidation of L-Lactate to Pyruvate where NAD acts as H+ acceptor.
- This reaction depends upon the:
- Buffers concentration.
- When there is an injury to the cells LDH spells into the bloodstream.
- LDH is the total measure of isoenzymes of LDH.
- LDH 1 indicates myocardial injury.
- LDH 2 indicate pulmonary injury.
- LDH 3 indicate pulmonary injury.
- Total LDH indicates multi-organ injury like :
- Myocardial infarction.
- Congestive heart failure causing pulmonary and hepatic congestion.
- Advanced malignancies.
- autoimmune diseases.
- Oxalate and Borate both inhibit the LDH enzyme activity.
- EDTA also inhibits this enzyme activity.
Table showing various isoenzymes in various tissues.
||3 and 2
||1 and 2
- Neonates = 415 to 690 U/L
- Adult = 140 to 280 U/L
- Adult = 100 to 190 U/L at 37 °C.
- Newborn = 160 to 450 U/L (30° C)
- Infants = 100 to 250 U/L.
- Child = 60 to 170 U/L
- Isoenzymes : Adult / elderly
- LDH 1 = 17 to 27 %.
- LDH 2 = 27 to 37 %.
- LDH 3 = 18 to 25 %.
- LDH 4 = 3 to 8 %
- LDH 5 = 0 to 5 %.
- The reference ranges are highly method dependent.
Raised LDH values are seen in:
- Liver disease:
- Ten times raised in toxic hepatitis with jaundice.
- LDH-5 is raised in the primary liver disease.
- LDH-5 is raised in case of liver anoxia.
- Lung diseases:
- Pulmonary infarction.
- In pulmonary embolism.
- Medication e.g. Warfarin, Antiepileptics.
- Myocardial Infarction
- LDH rises within 24 to 48 hours.
- Peak level is between 2 to 3 days.
- Return to normal is slow process may take 5 to 10 days.
- LDH may be raised moderately in the :
- Cardiac failure.
- Liver congestion.
- That is why the LDH level is helpful for the diagnosis of MI in the late stage, after 4 days of the history of chest pain.
- Malignant diseases:
- LDH levels are raised in lymphomas and liver cell necrosis.
- 70% of the cases with metastasis to the liver has raised LDH.
- Without metastasis to liver, it is raised in 20 to 60% of the cases.
- High levels are seen in the case of Hodgkin's disease, abdominal cancer, and lung.
- Leukemias has a moderate increase.
- Kidney diseases:
- It is raised in 1/3 cases of kidney diseases.
- Mostly in tubular necrosis.
- And in pyelonephritis.
- In case of renal infarction, the picture is like myocardial infarction.
- Muscular dystrophy:
- There is a moderate increase in the progressive muscular dystrophy particularly in the early and mid-stages of the disease.
- LDH-5 is mainly increased.
- After damage or loss of the large mass of the muscle, LDH level declines.
- Cerebrospinal fluid:
- Normally it is low than the serum.
- LDH-4 and LDH-5 are not found in the CSF.
- In bacterial meningitis, WBCs raise the level of LDH-4 and LDH-5.
- In the case of viral meningitis, the lymphocytes increase the level of LDH-1 and LDH-3.
- Total LDH raised the level in the urine indicates urologic injury.
- Three to five times raised level is seen in:
- Chronic glomerulonephritis.
- Systemic lupus erythematosus.
- Diabetic nephropathy.
- Urinary bladder and kidney tumors.
- LDH level may be done in the pleural, cardiac or peritoneal fluids to differentiate exudate or transudate.
- LDH isoenzymes increased in various diseases :
- LDH-1 increased in renal infarction.
- It is raised in the germ cell tumor-like seminoma and teratoma of the testes.
- And dysgerminoma of the ovary.
- LDH-3 increased in pulmonary infarction.
- LDH-3 and LD-4 increased in lymphoproliferative disorders.
- LDH-4 may be the main isoenzyme in acute lymphoblastic leukemia.
- Normal LDH-1: LDH-2 ratio = <0.80 while in the myocardial infarction is >0.80.
- LDH-1 > LDH-2 in hemolytic anemias and pernicious anemia.
As LDH is distributed in the multiple organs, so the total LDH is not a marker of specific disease or injury.
Serum LDH Isoenzymes in various diseases:
||LDH Isoenzymes raised
||I and II
|Pulmonary embolus without hemorrhage
|Pulmonary embolism with hemorrhage
||I, II, III
|Sickle cell crises
|Acute MI with congestion of the liver
Possible References Used
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