The Light criteria: the beginning and why they are useful 40 years later

Clin Chest Med. 2013 Mar;34(1):21-6. doi: 10.1016/j.ccm.2012.11.006. Epub 2013 Jan 17.


The Light criteria serve as a good starting point in the separation of transudates from exudates. The Light criteria misclassify about 25% of transudates as exudates, and most of these patients are on diuretics. If a patient is thought likely to have a disease that produces a transudative pleural effusion but the Light criteria suggest an exudate by only a small margin, the serum-pleural fluid protein gradient should be examined.

Publication types

  • Review

MeSH terms

  • Diagnosis, Differential
  • Diagnostic Techniques and Procedures / trends*
  • Exudates and Transudates / chemistry*
  • Humans
  • Light*
  • Pleural Effusion / diagnosis*