MEASUREMENT OF PLEURAL FLUID CHOLESTEROL AND LACTATE-DEHYDROGENASE - A SIMPLE AND ACCURATE SET OF INDICATORS FOR SEPARATING EXUDATES FROM TRANSUDATES

Objectives: To evaluate the usefulness of diverse combinations of pleu ral cholesterol concentration, pleural or serum protein, and lactate d ehydrogenase (LDH) levels for the differentiation of pleural exudates and transudates. Design: Prospective laboratory study of pleural effus ions. Setting: Medical school hospital. Patients: One hundred eighty c onsecutive internal medicine ward patients in whom the etiologic diagn osis of their pleural effusion was confirmed. Measurements: Cholestero l concentration in pleural fluid and protein and LDH both in pleural f luid and blood serum. Results: According to their etiology, 49 (27.2%) of the effusions were transudates and 131 (72.7%) were exudates. Usin g a cutoff point of 45 mg for pleural cholesterol and values for prote in and LDH of Light et al, the best diagnostic power corresponded to t he combination of pleural cholesterol and LDH: cholesterol level over 45 mg/dL and/or LDH over 200 IU/L identified exudates with a sensitivi ty of 99% and a specificity of 98%. All the other combinations showed inferior values and the criteria of Light ct al reached 98 and 82%, re spectively. Conclusions: The measurement of pleural cholesterol and LD H permits the separation of pleural exudates from transudates with an accuracy similar to the original report of Light et al, with the advan tage of requiring only two laboratory determinations and no simultaneo us blood sample.