Differential diagnosis of pleural fluid results
| PF results | Common causes |
|---|---|
| Low glucose and/or high LDH | Pleural infection, MPE, rheumatoid effusion, oesophageal rupture, lupus pleuritis and, at times, TPE |
| High protein levels | Exudative effusion and any aetiology, very high levels are often caused by TB |
| Very low protein (<15 g/dL) | Dural leak, urinothorax, entrapped lung |
| Lymphocyte predominance | TPE, lymphoma, post cardiac bypass graft, renal or liver failure, rheumatoid arthritis, rarely PPE |
| Neutrophil predominance | PPE, early TPE, less commonly due to pulmonary embolism or pancreatitis |
| Eosinophil predominance | MPE, idiopathic and PPE |
LDH = lactate dehydrogenase; MPE = malignant pleural effusion; PF = pleural fluid; PPE = parapneumonic effusions; TB = tuberculosis; TPE = tuberculous pleural effusion