CPPE is defined as non-purulent effusion in a patient with clinical evidence of infection such as fever and/or elevated blood leukocyte count and/or elevated CRP, with pleural fluid pH ≤ 7.2 (measured by blood-gas analyzer), or pleural fluid glucose < 60 mg/dl or pleural fluid LDH >1000 IU/L26. Empyema is defined as pus within the pleural space and/or presence of bacteria on pleural fluid Gram stain or culture.