Pleural fluid lysozyme in tuberculous and non-tuberculous pleurisy.

The series comprised 37 patients admitted to hospital for the diagnostic evaluation of one-sided or bilateral pleurisy. Patients with malignancies of extrapulmonary tissues were not included. The diagnosis of pleurisy was based on clinical, laboratory, and radiological findings. The patients were divided into three groups according to the final diagnosis: (a) those with tuberculous pleurisy, (b) those with non-tuberculous pleurisy (carcinoma, collagenosis, non-specific pleurisy, and pleural effusion of cardiovascular origin), and (c) those with bacterial empyema. Of the 12 tuberculous patients 10 had either a positive culture for Mycoplasma tuberculosis or a positive pleural biopsy finding, and in two the diagnosis was based on clinical and radiological findings. With EDTA used as anticoagulant, lysozyme activity was determined simultaneously in plasma and in cell-free pleural fluid with the lysoplate method in which purified human lysozyme was the standard.' Lysozyme concentrations in both plasma and pleurial fluid were significantlv higher in patients with tuberculous pleurisy than in those with non-tuberculous pleurisy (see table). Moreover, the pleural fluid concentration of lysozyme in patients with tuberculosis was significantly higher than the plasma concentration (P<0 001). In 11 out of 12 tuberculous patients but none of the 22 non-tuberculous patients either the concentration of pleural fluid lysozyme was 18-0 mg/l or greater or the pleural fluid:plasma lysozyme ratio was 1 5 or greater. In three patients with bacterial empyema of the pleural cavity lysozyme activity in pleural fluid was raised considerably. In no group of patients did the lysozyme levels in the pleural fluid correlate either with the total number of cells or with the number of non-lymphoid cells in the pleural effusion.