Acid glycosaminoglycans (mucopolysaccharides) in the differential diagnosis of pleural effusion.

Pleural fluid glycosaminoglycans (GAG) in 64 patients with various diseases were isolated by anion-exchange chromatography after proteolysis, and characterised by spectrophotometric, electrophoretic and enzymatic techniques. GAG concentrations ranged from 7 to 1178 microng hexuronate/ml pleural fluid. The highest values (1178, 161 and 160 micron/ml) were found in patients with diffuse mesothelioma. Over 90% of the pleural fluid GAG consisted of hyaluronic acid (HA) in these patients. In other types of pleural effusion the relative HA content varied from 42 to 70% of the total GAG. Determination of pleural fluid HA consequently appears extremely valuable in the diagnosis of the form of mesothelioma producing HA. The mean GAG concentration of pleural fluid was significantly higher in tuberculous pleurisy than in hydrothorax (P less than 0.01), secondary malignant pleural effusion (P less than 0.0005) and idiopathic pleurisy (Pless than 0.03). It was impossible to demonstrate definite correlations between GAG and protein, and GAG and glucose concentrations of pleural fluid.