The characteristics of pleural effusion are as follows: pH, 7.8; specific gravity, 1.035; total protein, 5.2 g/dL; glucose, 120 mg/dL; adenosine deaminase (ADA), 18.8 U/L; LDH, 292 U/L; amylase, 19 U/L; carcinoembryonic antigen (CEA), 3.2 ng/mL; carbohydrate antigen 19–9 (CA19–9), < 5.0 U/mL. Here, ADA is linked to Pleural effusion.