Clinical significance of the isomorphic pattern of the isoenzymes of serum lactate dehydrogenase

Five hundred patients with the isomorphic pattern of the isoenzymes of serum lactate dehydrogenase (LDH) were surveyed. The isomorphic pattern of LDH isoenzymes is defined as a significant increase of total LDH with normal or low percentage of individual fractions, but with the LDH1:2 ratio less than unity. Diagnoses were, in descending order of frequency, cardiorespiratory diseases, malignancy, fracture, diseases of the central nervous system, infection/inflammation, hepatic cirrhosis and/or alcoholism, trauma without fracture, infectious mononucleosis, hypothyroidism, uremia, necrosis, pseudomononucleosis, viremia and intestinal obstruction. Incidence of increased serum activity in individuals without evidence of disease or drug explanation was 3 percent. Low PaO2 was observed in 88 percent of the 67 patients in whom it was measured.