[The diagnostic usefulness of cholinesterase in pleural exudates].

BACKGROUND AND OBJECTIVES

The pleural fluid/serum cholinesterase ratio (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 pleural exudates.

MATERIALS AND METHODS

A total of 167 patients with the diagnosis of pleural exudate were studied: 74 carcinomatous, 32 tuberculous, 31 parapneumonic, 30 other causes. Pleural fluids were divided on the basis of lymphocyte or polymorphonuclear predominance and were grouped according to diagnosis. The PF/S cholinesterase ratio was determined in all patient.

RESULTS

In lymphocytic exudates, when PF/S ratio was < 0.42 pleural effusion was classified as malignant, with a sensitivity (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 pleural effusions, a ratio > or = 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 diagnosis 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 cellular predominance in the pleural fluid.