Evaluate cause. A thoracentesis involves removing fluid from the pleural cavity. Laboratory values obtained from the fluid may enable a doctor to determine the cause of the fluid accumulation. Amylase present in the fluid could mean either pancreatitis or, more rarely, esophageal perforation. Glucose<40mg/dl, possible infection, >40mg/dl probably not infectious.
Fluid. Amylase is to test to see if it is related to the pancreas. The glucose can help determine if it is related to infection.
Cancer & infections. A few possible causes of increased pleural fluid amylase level are cancer, pancreatitis, liver cirrhosis and tuberculous infection. Cancer is more commonly and is more likely with high amylase level. Pleural fluid glucose helps in certain infections from noninfectious causes of pleural effusions.