Characteristics of Pleural Exudates

• Pleural fluid protein level >3 g/dL^a
• Pleural fluid to serum protein ratio >0.5
• Pleural fluid lactate dehydrogenase (LDH) level >200 U
• Pleural fluid to serum LDH ratio >0.6
• Pleural fluid pH >7.3
• Pleural fluid specific gravity >1.016

^a Transudates have opposite sign (less than cutoff) for values listed for exudates (e.g., pleural fluid protein level <3 g/dL).

Adapted from Erasmus JJ, et al. Management of malignant pleural effusions and pneumothorax. Radiol Clin North Am 2000;38:375–383.