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February 1974

Serum Enzymes and IsozymesExtrapulmonary Sources in Acute Pulmonary Embolism

Arch Intern Med. 1974;133(2):243-246. doi:10.1001/archinte.1974.00320140081008

The diagnostic use of serum enzyme determinations was evaluated in 33 patients with pulmonary embolisms. The level of serum glutamic oxaloacetic transaminase (SGOT) was elevated in one third and lactate dehydrogenase (LDH) activity was elevated in two thirds of the patients. Elevations of serum LDH activity depended substantially on increases in either LDH1 or LDH5 isozymes. In conjunction with increases of serum ornithine transcarbamoylase and α-hydroxybutyrate dehydrogenase activity, these findings indicate extrapulmonary enzyme release into the serum. Most probable enzyme sources are the liver and erythrocytes. Serum creatine kinase level was elevated in five of 22 patients studied, its elevation depending totally on the muscle type (MM) isozyme. The BB isozyme of lung tissue was not found in any of these patients. These results indicate that serum enzyme determinations are of little value in diagnosing pulmonary embolism.