| Location |
| Right side (73 to 85%) |
| Left side (13 to 17%) |
| Bilateral (2 to 10%) |
| Fluid |
| Cell count <250 polymorphonuclear cells per mm3 |
| Protein <2.5 g/dL |
| Pleural fluid/serum total protein ratio <0.5 |
| Pleural fluid/serum lacate dehydrogenase ratio <0.6 |
| Serum-to-pleural fluid albumin gradient >1.1 g/dL |
| Pleural fluid/serum bilirubin ratio <0.6 |
| pH >7.4 |
| Glucose level similar to that of serum |
