DIAGNOSTIC USEFULNESS OF CHOLINESTERASE I N PLEURAL EXUDATES

Background and objectives. The pleural fluid/serum cholinesterase rati o (PF/S) is the most efficient parameter to differentiate transudates from exudates. The objective of this study was to evaluate whether its determination might yield additional diagnostic information in pleura l exudates. Materials and methods. A total of 167 patients with the di agnosis of pleural exudate were studied: 74 carcinomatous, 32 tubercul ous, 31 parapneumonic, 30 other causes. Pleural fluids were divided on the basis of lymphocyte or polymorphonuclear predominance and were gr ouped according to diagnosis. The PF/S cholinesterase ratio was determ ined in all patient. Results. In lymphocytic exudates, when PF/S ratio was < 0.42 pleural effusion was classified as malignant, with a sensi tivity (S) of 56% (95% CI: 43%-66%) and a specificity (SP) of 90% (95% CI: 78%-95%). For the diagnosis of tuberculosis, in the total of pleu ral effusions, a ratio greater than or equal to 0.45 showed a S of 97% (95% CI: 82%-99%) and a SP of 51% (95% CI: 42%-59%). Conclusions: The PF/S cholinesterase ratio yielded an useful information on the diagno sis of pleural exudates. Thus, in our series of patients, a ratio < 0. 42 in a lymphocytic effusion suggested a malignant origin, and a ratio < 0.45 practically ruled out tuberculosis, irrespective of the cellul ar predominance in the pleural fluid.