The lactate dehydrogenases in malignant and non-malignant diseases

The objective of this paper was to determine different patterns of Lactate Dehydrogenase(LD) isoenzymes in serum, pleural effusions and ascitic fluid collections and their usefulness in the differential diagnosis of malignant and non-malignant diseases. It was a case control study carried out at the Lagos University Teaching Hospital. Forty- six patients with pleural or ascitic fluid collection (male and female, age range between 18 and 65 years) made up of Twenty-two patients with malignant diseases and twenty-four with non- malignant diseases were recruited. Control group comprised 50 apparently healthy subjects of both sexes with age ranging between 18 and 65 years. Serum, pleural and ascitic fluid collections were assayed for total lactate dehydrogenase(LD) and it s isoenzymes. Total LD was estimated using the pyruvate to lactate reaction. LD isoenzyme analysis was estimated by cellulose acetate electrophoresis and stained with formazan. The mean total serum LD activity in the disease groups (malignant and non-malignant) was significantly higher than the mean total serum LD activity in the control group. The pleural fluid LD was highest in patients with empyema thoracis. Five isoenzymes of LD (LD1 - LD5) were present in both control and patient sera. The serum LD1 and LD2 isoenzymes were predominant in the controls. The serum LD4 and LD5 isoenzymes were predominant in the disease groups (malignant and non-malignant). LD4 and LD5 were the predominant isoenzymes in both pleural and ascitic fluids obtained in malignant and non-malignant diseases. Serum LD4 was significantly higher than serum LD5 in non-malignant disease while serum LD5 was significantly higher than serum LD4 in malignant disease. The types of malignancies could not be differentiated by serum and effusion fluid LD isoenzyme pattern. Pleural fluid total LD estimation is useful in monitoring patients on chest tubes and may be used to determine when to insert them. Serum LD4 and LD5 differentiates malignant from non-malignant disease but the effusion LD isoenzyme pattern does not.