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Pleural effusion - summary of tests to consider

Protein

LDH

Glucose - <3.3mmol/L associated with empyema, rheumatoid disease, SLE, TB, malignancy

pH - <7.2 indicates pleural infection and is an indication for drainage if parapneumonic

WCC and differentials

  • Neutrophils - PE, pancreatitis, pneumonia, empyema

  • Lymphocytes - Cancer, TB pleuritis, CCF

  • Eosinophila – Pneumothorax, haemothorax, asbestosis, Churg-Strauss

  • Mononuclear cells - Chronic inflammatory process

Cytology – malignant effusions

Amylase – not routine. Useful in oesophageal rupture or effusions associated with pancreatic disease

HCT – suspicion of haemothorax

Gram stain and culture – use blood culture bottles and specimen jars, especially if chronic illness or suspect TB or fungus

Remember to take serum protein and LDH for comparison

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