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