USEFULNESS OF SOLUBLE INTERLEUKIN-2 RECEPTOR IN DIFFERENTIATING TUBERCULOUS AND CARCINOMATOUS PLEURAL EFFUSIONS

Objective: To evaluate the usefulness of soluble interleukin 2 recepto r (sIL-2R) in differentiating tuberculous and carcinomatous pleural ef fusions. Methods: Levels of sIL-2R were measured simultaneously in pla sma and pleural fluid in 111 patients with pleural effusions of unknow n causes. Results: The causes of pleural effusions were tuberculosis i n 42 cases, carcinoma in 41 cases, pneumonia in 18 cases, and heart fa ilure in 10 cases. In all groups of patients, sIL-2R levels were signi ficantly higher in pleural fluid than in plasma. Plasma and effusion l evels of sIL-2R were highest in the patients with tuberculosis, follow ed by those with carcinoma, pneumonia, and heart failure. Levels were significantly higher in the tuberculous group than in the carcinomatou s group. To differentiate tuberculous from carcinomatous effusions, th e highest plasma and effusion sIL-2R values obtained from the carcinom atous group were chosen as cutoff points (test specificity, 100%). The sensitivities of plasma and effusion sIL-2R levels in differentiating tuberculous and carcinomatous pleural effusions were 50% (21 of 42 sa mples) and 81% (34 of 42 samples), respectively. Conclusions: Although increased plasma and pleural fluid levels of sIL-2R should not be vie wed as a diagnostic test specific for tuberculous pleural effusion, sI L-2R level appears to be clinically useful as a biochemical marker to differentiate tuberculous and carcinomatous pleural effusions.