Is it Meaningful to use Biochemical Parameters to Discriminate Between Transudative and Exudative Pleural Effusions

Objectives The usefulness of biochemical criteria to separate pleural transudates from exudates is controversial, and the limitations of Light’s criteria in patients receiving diuretic therapy is of general concern. We evaluated the added value of biochemical criteria to clinical judgment for separating transudates from exudates. Setting A community teaching hospital. Design A prospective, observational study for the evaluation of diagnostic tests. Patients and measurements In 249 consecutive patients referred for diagnostic thoracentesis, two physicians classified the pleural effusion as transudate or exudate based on all available information just before performing the thoracentesis. The sensitivity, specificity, and accuracy of the clinical presumption were compared with those of Light’s criteria, and serum-pleural fluid albumin and protein gradients. The combined accuracy of biochemical and clinical criteria was also assessed. Results The accuracy of Light’s criteria (93%) was significantly higher than that showed by the initial clinical presumption (84%; p Conclusions Light’s criteria are significantly superior to the clinical presumption to separate pleural transudates from exudates. In patients receiving diuretics, Light’s criteria lose accuracy, which is similar to that showed by the use of alternative biochemical criteria alone or combined with clinical judgment.