Pleural fluid smear is a laboratory procedure to check for bacteria, fungi, or abnormal cells in the fluid that may be found in the space around the lungs (called a pleural effusion).
How the test is performed
A health care or laboratory technician provider examines a sample of pleural fluid under the microscope. If the smear detects bacteria or fungi, other methods may be used to further identify those organisms.
How the test will feel
The sample is obtained through a procedure called thoracentesis. For information about this test and its risks, see thoracentesis.
Why the test is performed
The test is performed if you have a pleural effusion and its cause is not known, especially if the health care provider suspects an infection or cancer.
Normally, no bacteria, fungi, or cancer cells are present in the pleural fluid.
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean
Positive results may indicate that infection, or cancer cells, is present. Other tests can help identify the specific type of infection or cancer. Sometimes, the test may show abnormalities from conditions such as systemic lupus erythematosus.
Broaddus VC, Light RW. Pleural effusion. In: Mason RJ, Broaddus VC, Martin TR, et al, eds. Murray and Nadel’s Textbook of Respiratory Medicine. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 73.
McCool FD. Diseases of the diaphragm, chest wall, pleura, and mediastinum. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 99.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Denis Hadjiliadis, MD, Assistant Professor of Medicine, Division of Pulmonary, Allergy and Critical Care, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.