- If at least one of the following three criteria is fulfilled, the fluid is defined as an exudate
- Pleural fluid-to-serum protein ratio greater than 0.5
- Pleural fluid-to-serum ԼDH ratio greater than 0.6
- Pleural fluid LDН greater than 0.67 (ie, two-thirds) the upper limits of the laboratory’s normal serum LDН
- High protein and LDH is associated with exudate