Discrimination of tuberculous from carcinomatous pleural effusion by biochemical markers: Adenosine deaminase, lysozyme, fibronectin and carcinoembryonic antigen.
We measured adenosine deaminase (ADA), lysozyme, fibronectin and carcinoembryonic antigen (CEA) in the pleural fluid of tuberculous and carcinomatous pleural effusion in order to discriminate these two groups. Tuberculous pleural effusion had significantly higher levels of ADA and lysozyme than did carcinomatous effusion. When ADA activity of more thn 33 IU/l is considered, diagnostic tests of tuberculous effusions showd a sensitivity of 100%, specificity of 95% and accuracy of 96%. A pleural fluid/serum ADA ratio (pl-ADA/s-ADA) above 1.1 was found in 100% of tuberculous and in 53% of carcinomatous effusions (sensitivity 100%, specificity 47%, diagnostic accuracy 70%). A lysozyme level above 12 .mu.g/ml, selected as the discriminating limit, was found in 100% of tuberculous and in 17% of carcinomatous effusions (sensitivity 100%, specificity 83%, diagnostic accuracy 83%). Pleural fluid/serum lysozome ratio (PL/SL) was also valuable in the discrimination of these two groups. When the cut-off level of 1.2 was considered, diagnostic tests of tuberculous effusions showed a sensitivity of 100%, specificity of 88% and accuracy of 93%, respectively. The mean fibronectin concentration in pleural fluid with tuberculous effusion was significantly higher than that in carcinomatous effusion, but there was a marked overlap between these two groups. On the other hand, CEA was significantly higher in carcinomatous effusions than in tuberculous effusions. At a cut-off level of 5 ng/ml, 53% of patients with carcinomatous effusion showed elevated pleural fluid CEA levels, while none of the tuberculous effusion did (sensitivity 53%, specificity 100%, diagnostic accuracy 65%). The combined assay of ADA, lysozyme, pl-ADA/s-ADA, PL/SL and CEA provide valuable information in the differential diagnosis between tuberculous and carcinomatous effusion, while fibronectin concentration can not be considered to have a definite diagnostic value.