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Light’s Criteria (for Exudative Pleural Effusions)

Pleural fluid protein
Serum protein
Pleural fluid lactate dehydrogenase (LDH) IU/L
Serum LDH IU/L
Upper limit of normal serum LDH
(based on laboratory reference range)
IU/L
Result:

 

Formula
The effusion is exudative if one of the Light’s criteria has been met:

  • Pleural fluid protein/serum protein ratio > 0.5.
  • Pleural fluid LDH/serum LDH ratio greater than > 0.6.
  • Pleural fluid LDH level greater than 2/3 of upper limit of normal LDH level in serum.