Lactic Acid Dehydrogenase (LD / LDH)

Elevated serum levels of LDH have been observed in a variety of disease states. The highest levels are seen in patients with megaloblastic anemia, disseminated carcinoma, and shock. Moderate increases occur in muscular disorders, renal diseases, and cirrhosis. Mild increases in LDH activity have been reported in cases of myocardial or pulmonary infarction, leukemia, hemolytic anemia, and nonviral hepatitis.2 Hemolysis elevates LDH results, oxalate inhibits LDH, and ascorbic acid can decrease LDH values. In infectious mononucleosis, LD is usually more elevated than AST, and there is usually an isomorphic pattern of LD isoenzymes. In viral hepatitis, by contrast, AST and ALT (the transaminases) are much more increased than is LD, about three or more times higher than total LD, and LDH is high. The differential diagnosis of acute infarct of myocardium includes pericarditis and angina, entities in which enzymes are usually not substantially increased. Bovine or porcine heparin therapy can cause increases in AST, ALT, and LD, with elevated LD hepatic fractions.2

1. LabCorp internal studies. 2. Tietz NW. Clinical Guide to Laboratory Tests. 4th ed. Philadelphia, Pa: WB Saunders Co; 2006.