Pleural fluid Gram stain

Definition

The pleural fluid Gram stain is a test to diagnose bacterial infections in the lungs.

Alternative Names

Gram stain of pleural fluid

How the test is performed

Pleural fluid is found in the space around the lungs. In a variety of diseases, an abnormal amount of pleural fluid builds up in the lungs.

A sample of the pleural fluid is needed for this test. For information on how the sample is obtained, see: Thoracentesis

The fluid sample is placed onto a microscope slide and mixed with a violet stain (called a Gram stain). A laboratory specialist uses a microscope to look for bacteria on the slide. If bacteria are present, the color, number, and structure of the cells are used to identify the specific organism.

How to prepare for the test

How the test will feel

See: Thoracentesis

Why the test is performed

The test is performed when the health care provider suspects an infection of the pleural space, or when a chest x-ray reveals an abnormal collection of pleural fluid.

Normal Values

Normally, no organisms 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

You may have a bacterial infection of the lining of the lungs (pleura).

What the risks are

References

Celli BR. Diseases of the diaphragm, chest wall, pleura, and mediastinum. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 100.