Routine measurement of pleural fluid amylase is not indicated

Background: The routine measurement of pleural fluid amylase is frequently recommended, but the cost-effectiveness of this procedure is unknown. Methods: To assess the utility of routine measurement of pleural fluid amyl ase in evaluating pleural effusions, we measured amylase, glucose, lactate dehydrogenase, and protein levels and blood cell counts in 379 patients und ergoing thoracentesis during a 22-month period from 1997 to 1999. Of these, 199 had effusions after cardiac surgery; 61, malignant; 48, transudative; 28, parapneumonic; 2, chylous; 2, rheumatoid; 1, tuberculous: and 1, from c hronic pleuritis. There were 37 exudates of unknown origin. Results : Measurement of pleural fluid amylase levels did not assist in det ermining the origin of the effusion in any of the patients. Amylase levels greater than 100 U/L (normal serum level in our laboratory is 30-110 U/L) w ere found in 5 (1.3%) of 379 patients: 1 patient with congestive heart fail ure (amylase, 173 U/L), 2 with post-cardiac surgery effusions (144 U/L and 130 U/L), 1 with pneumonia (109 U/L), and 1 with lung cancer (105 U/L). Conclusions: The routine measurement of pleural fluid amylase levels is nei ther clinically indicated nor cost-effective. We suggest that pleural fluid serum amylase levels be measured only if there is a pretest suspicion of a cute pancreatitis, chronic pancreatic disease, or esophageal rupture.