EBF	Criterion	Interpretation
Pleural fluid	Light’s criteria: 1. pleural fluid/serum protein ratio > 0.5; 2. pleural fluid/serum LD ratio > 0.6 3. absolute pleural fluid LD activity > 2/3 of serum URL	Exudative effusion if at least one criterion is met.
	serum-pleural fluid albumin gradient ≤ 12 g/L	If clinical symptoms suggest transudative pleural effusion, but Light’s exudative criteria are met (usually by a small margin), the albumin gradient (calculated as the serum albumin concentrations minus pleural fluid albumin concentration) should be used as a tool to confirm true transudative pleural effusions. An albumin gradient > 12 g/L is indicative of transudates, while exudates have an albumin gradient ≤ 12 g/L.
	cholesterol > 1.2 mmol/L	A pleural fluid cholesterol cut-off point of > 1.2 mmol/L is accepted for the identification of exudates.
	pleural fluid/serum cholesterol ratio > 0.3	Exudative effusion.
	LD > 0.45 serum URL and cholesterol > 1.2 mmol/L	The paired combination of pleural fluid LD and pleural fluid cholesterol yielded a 98% specificity and 72% sensitivity in identifying exudates. An exudative effusion is identified if both criteria are met.
	protein > 29 g/L, LD > 0.45 serum URL and cholesterol > 1.2 mmol/L	This triplet of pleural fluid tests yielded a sensitivity of 98% and specificity of 70% in discriminating exudates from transudates. An exudative effusion is identified if all criteria are met.
	total WBC count > 1000 x106/L with neutrophil predominance (≥ 50% of total WBC)	Acute pleural inflammation, bacterial pneumonia, pancreatitis, early tuberculosis.
	total WBC count > 1000 x106/L with lymphocyte predominance (≥ 50% of total WBC)	Tuberculosis, viral infection, malignancy, chylothorax, rheumatoid pleuritic.
	total WBC count > 1000 x106/L with eosinophilia (> 10% of total WBC)	Pneumothorax, malignancy, haemothorax, pulmonary infarction, congestive heart failure.
	pleural fluid to serum amylase ratio > 1	Pancreatitis, malignancy, oesophageal rupture, pancreatic pseudocyst, liver cirrhosis, cardiac failure, parapneumonic effusion, ruptured ectopic pregnancy, trauma.
	ADA ≥ 40 U/L	Differentiation of tuberculous and malignant pleuritis.
	pH < 7.20 (and pleural fluid LD > 3 serum URL)	Complicated parapneumonic effusion.
	triglycerides ≥ 1.2 mmol/L and cholesterol < 5.2 mmol/L	Chylous effusions.
	pleural fluid to serum creatinine ratio > 1	Urinothorax.
Pericardial fluid	Light’s criteria: 1. pericardial fluid/serum protein ratio > 0.5; 2. pericardial fluid/serum LD ratio > 0.6 3. absolute pericardial fluid LD activity > 2/3 of serum URL	Exudative effusion if at least one criterion is met.*
	serum-pericardial fluid albumin gradient ≤ 12 g/L	Exudative effusion.*
	cholesterol > 1.2 mmol/L	Exudative effusion.*
	ADA ≥ 40 U/L	Tuberculous pericarditis.
Peritoneal fluid	SAAG < 11 g/L	Low-albumin gradient effusions (i.e. exudative).
	neutrophil count ≥ 250 x106/L	Spontaneous bacterial peritonitis.
	ascitic to serum triglycerides ratio > 1	Chylous ascites.
	peritoneal fluid to serum amylase ratio > 1	Pancreatic ascites, gut perforation, ruptured pseudocysts and mesenteric thrombosis.
	ADA ≥ 39 U/L	Tuberculous peritonitis.
EBF – extravascular body fluid. LD – lactate dehydrogenase. URL – upper reference limit. WBC – white blood cells. ADA - adenosine deaminase. SAAG – serum-ascites albumin gradient. *Due to limited evidence, results should always be correlated with clinical symptoms.