Box 1.

Light's criteria for exudative effusions

Exudative effusions will have one or more of the following.

  • Pleural fluid protein / serum protein >0.5.

  • Pleural fluid LDH / serum LDH >0.6.

  • Pleural fluid LDH >2/3 serum LDH upper limit of normal.

  • LDH = lactate dehydrogenase.