Accuracy of seven criteria based on cholesterol and lactate dehydrogenase for differentiating exudative and transudative pleural effusions

Previous studies have proposed multiple diagnostic criteria based on cholesterol and lactate dehydrogenase (LDH) levels to differentiate pleural exudates from transudates. However, these criteria have not been widely validated, and no study has compared their diagnostic accuracies within the same population. This study recruited patients from retrospective (BUFF) and prospective (SIMPLE) cohorts. Pleural biopsy, microbiological culture, and effusion cytology were used to verify the causes of exudates or transudates. The diagnostic accuracy of pleural cholesterol and LDH levels in identifying exudates was evaluated using receiver operating characteristic (ROC) curves. Subsequently, the accuracies of seven previously reported cholesterol- and LDH-based classification criteria were compared with those of Light's criteria. Pleural fluid cholesterol levels and LDH activity were significantly higher in exudates than in transudates. The area under the ROC curve (AUC) for pleural fluid cholesterol and LDH levels was 0.90 (95% CI: 0.86-0.94) and 0.87 (95% CI: 0.82-0.92) in combined cohort, respectively. We found that the diagnostic accuracy of the combination of pleural fluid cholesterol > 1.04 mmol/L (40 mg/dL) or pleural LDH > 0.6 upper limit of serum LDH reference interval was comparable to that of Light's criteria, whereas the other criteria were less accurate. Combining pleural fluid cholesterol and LDH levels using the preceding thresholds has comparable accuracy to Light's criteria for separating exudates from transudates.