- The clinical utility of LDH and its isoenzyme assays include:
- Aids in the evaluation of myocardial infarction (MI) or extension thereof (has been mostly replaced by CPK, CPK-MB, Troponins, Myoglobin)
- Determine the degree of muscle wasting in muscular dystrophy
- Evaluation of conditions such as:
- Anemia (esp. hemolytic)
- Hepatic diseases
- Muscular dystrophy
- Myocardial infarction
- Pulmonary infarction
- Red blood cell hemolysis
- Renal infarction
- Determine chronicity of liver, lung, and kidney disorders
- Assists in the diagnosis of P. cariniipneumonia in HIV patients
- Evaluation and monitoring the effectiveness of cancer chemotherapy
- Serial estimation of LDH helps in detecting recurrence of cancers such as Ewing's sarcoma, acute lymphocytic leukemia, non-Hodgkin's lymphoma
- LDH and its isoenzymes, LDH-1 and LDH-2, are released in the blood after acute myocardial infarction (MI) within the first 8-12 hours, peaks at 24-72 hours, and remain elevated for 7 to 12 days
- Reversal of the LDH-1:LDH-2 ratio is seen within 48 hours of the infarction also referred to as 'flip' isoenzyme pattern. Persistent LD-1:LD-2 flip after acute MI may represent reinfarction (LDH estimation is replaced by CPK and troponin assays)
- The LDH isoenzyme pattern of hemolytic, megaloblastic, and sickle cell anemia is similar to MI as RBCs have same isoenzyme pattern as that of heart muscle, but the time elapsed to peak values may help to differentiate these conditions
- LDH-1:LDH-2 flip or inversion also seen in red cell hemolysis and renal infarction
- The mid-zone LDH isoenzymes (LD-2, LD-3 and LD-4) are elevated in most cancers, massive platelet destruction as in pulmonary embolism or post-transfusion period, and in lymphatic system disorders as in infectious mononucleosis, lymphomas, lymphocytic leukemias
- LD-5 increase is more significant when LD5/LD4 ratio is increased especially in muscular dystrophy, where the levels rise early and approach normal as muscle mass is reduced by atrophy
- Total LDH level is used as a prognostic indicator in metastatic colorectal carcinoma, where initial normal levels of LDH versus those with an abnormal level of LDH had median survivals of 16 versus 7 months respectively
- Elevated levels of LDH within 24 hrs of chest pain onset that plateaus off in 1–2 days, along with normal SGOT levels (serum glutamic oxaloacetic transaminase) is indicative of pulmonary infarction
- Serum LDH levels are helpful to distinguish pulmonary toxoplasmosis from P. cariniipneumonia in HIV infected persons
- LDH levels are not elevated in angina and pericarditis
- Decreasing LDH levels are indicative of positive response to cancer therapy
- Some of the characteristic patterns of LDH isoenzymes include:
- Elevated LD-1 and LD-2
- Hemolytic anemia
- Megaloblastic anemia
- Myocardial infarction
- Muscular dystrophy
- Elevated LD-2 and LD-3
- Extensive carcinomatosis
- Granulocytic leukemia
- Pancreatitis
- Elevated LD-4 and LD-5
- Congestive heart failure
- Pulmonary infarction
- Toxic hepatitis
- Viral hepatitis
Additional information
- LDH isoenzymes should be interpreted in light of the clinical situation. Isoenzymes are usually not performed if the total LDH is less than 130 IU/L
- If LDH level in the body fluid is equal to or greater than that of the LDH serum, it is suggestive of an inflammatory process
- Factors interfering with test results include:
- Strenuous exercise and the muscular exertion
- Recent childbirth
- Extensive skin diseases
- Hemolysis of RBCs due to freezing, heating, or shaking the blood sample (elevation of LDH-1 and LDH-2 and destruction of LDH-4 and LDH-5)
- Failure to draw sample on schedule for evaluation of acute MI
- Failure to send sample to lab immediately
- Failure to centrifuge sample and separate cells from serum
- Recent surgery or pregnancy
- Prosthetic heart valve (due to chronic hemolysis)
- Changes in temperature inactivates LD-5
- Related laboratory tests include:
-glutamyltranspeptidase- Apolipoprotein A
- Apolipoprotein B
- Aspartate aminotransferase
- Atrial natriuretic peptide
- Blood gases
- B-type natriuretic peptide
- Calcium (blood and ionized)
- Cholesterol (total, HDL, and LDL)
- C-reactive protein
- Creatine kinase and isoenzymes
- Glucose
- Homocysteine
- Ketones
- Lipoprotein electrophoresis
- Magnesium
- Myoglobin
- Pleural fluid LDH
- Potassium
- Triglycerides
- Troponin I
- Troponin T