Differentiating Pleural Effusions: Criteria Based on Pleural Fluid Cholesterol

Objective: To assess the efficacy of pleural fluid cholesterol in differentiating transudates and exudates as compared with Light’s criteria.
Methods: Patients with pleural effusion during a 6-month period were enrolled in the study and underwent thoracentesis. Pleural fluid was analyzed for the levels of protein, lactate dehydrogenase (LDH), and cholesterol. Etiological diagnosis, which was established after considering clinical and biochemical factors, was the gold standard for comparison. Cut-off values for pleural fluid cholesterol were taken as 60 mg/dL and 45 mg/dL.
Results: A total of 53 patients were included for final analysis. Of them, 19 were with transudates and 34 with exudates in their pleural fluids. The sensitivity, specificity, positive predictive value, and negative predictive value of the pleural fluid cholesterol (cut-off >45 mg/dL) were 97.06%, 94.74%, 97.06%, and 94.74%, respectively, for identifying exudates. These values were differentiating better than those obtained by Light’s criteria for pleural fluid cholesterol (cut-off >60 mg/dL) (p<0.0001). Combining pleural fluid protein with pleural fluid cholesterol (>45 mg/dL) gave a higher specificity (100%) and positive predictive value (100%) but a lower sensitivity (82.93%) and negative predictive value (63.16%).
Conclusion: Pleural fluid cholesterol is better than Light’s criteria for the differentiation of transudates and exudates and is less cumbersome as it does not require a simultaneous blood sampling. Cut-off value of pleural fluid cholesterol for differentiating transudates and exudates should be 45 mg/dL. Further studies are warranted to assess the efficacy of the combination of pleural fluid protein and cholesterol as criteria for classifying effusions.