Comparative analysis of pleural fluid biochemical parameters with cholesterol to differentiate transudates from exudates

Background: Light′s criteria is the gold standard to differentiate transudative pleural effusion (PE) from exudative PE, but it requires four biochemical estimations which, in developing countries such as India, may not be feasible in every patient due to economic constraints. Aims: To evaluate the comparative usefulness of pleural fluid biochemical parameters with relative usefulness of pleural cholesterol to the traditional Light′ criteria. Setting and Design: Prospective institutional based study. Materials and Methods: A total of 56 cases of PE were studied consecutively, of which 34 cases were of tuberculous effusion and 22 cases of nontubercular effusion. The data obtained from the patients were collected, analyzed, and observations noted down. Statistical Analysis: Sensitivity, specificity, positive predictive value and negative predictive value of different biochemical parameters single or in combination were analyzed by SPSS 16 software. Results: According to their etiology, 7 of the effusions were transudates and 49 were exudates. Using a cutoff point of 45 mg for pleural cholesterol and values for protein and lactate dehydrogenase (LDH) of Light et al., the best diagnostic power corresponded to the combination of pleural cholesterol and LDH; cholesterol level over 45 mg/dL and/or LDH over 200 IU/L differentiate exudates from transudates with a sensitivity of 99% and a specificity of 98%. Conclusions: The measurement of pleural cholesterol and LDH permits the separation of pleural exudates from transudates with accuracy similar to the original report of Light et al., with the advantage of requiring only two laboratory determinations and no simultaneous blood sample, especially in a country like India where financial and technical constraints are immense