Light's criteria calculator

Light's Criteria

Light's Criteria — Pleural Effusion

Parameter	Value
Pleural fluid protein (g/dL)
Serum protein (g/dL)
Pleural fluid LDH (IU/L)
Serum LDH (IU/L)
Upper limit of normal serum LDH (IU/L)
Results
Pleural protein / Serum protein ratio
Pleural LDH / Serum LDH ratio
Pleural LDH / ULN serum LDH

Interpretation
Exudative (any 1 of:)	Pleural protein/serum protein > 0.5 OR Pleural LDH/serum LDH > 0.6 OR Pleural LDH > 2/3 ULN serum LDH. Causes: infection, malignancy, PE, autoimmune, etc.
Transudative	None of the above criteria met. Causes: CHF, cirrhosis, nephrotic syndrome, PE.

References
Light RW, Macgregor MI, Luchsinger PC, et al. Pleural effusions: the diagnostic separation of transudates and exudates. Ann Intern Med. 1972;77(4):507-513. PMID 4642731.