Light’s Criteria for Exudative Effusions

HealthCare

Light’s criteria (= Exudate Criteria) are 99.5% sensitive for diagnosing exudative effusions and differentiate exudate from transudative effusions in 93-96% of cases.

Light’s criteria  for fluid being exudate are:

  • Pleural fluid protein to serum protein ratio > 0.5,
  • Pleural fluid LDH to serum LDH ratio > 0.6, and/or
  • pleural LDH > 2/3rds (i.e. 0.67 times) the upper limit of normal for serum LDH)

NB: 0.67 = 2/3

Light’s Criteria Calculator.

Mnemonic. Exude Light. Light’s criteria define an exudative solution. If the criteria are not fulfilled, then the solution is a transudate.

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