<prompt> Answer this question truthfullyWhat are Lights criteria for exudative pleural effusions?  <response>: <reason> Exudative pleural effusions must meet one of Lights criteria, which are: Pleural proteinserum protein 0.5, Pleural LDHserum LDH 0.6, or Pleural LDH 23 upper limit of normal serum LDH. 