Sputum direct fluorescent antibody (DFA) is a test that looks for microorganisms in lung secretions.

Your doctor may order this test if you have signs of certain lung infections or pneumonias.

You will produce a sputum sample from your lungs by coughing up mucus from deep inside your lungs. (The mucus is not the same as saliva or spit from the mouth.)

In the laboratory, antibodies that have been chemically linked to a fluorescent dye are added to the sample. These antibodies are considered "flagged." They will attach to specific antigens -- in this case, the microorganism against which they were formed. If the specific microorganism is present, a bright glow (fluorescence) can be seen in the sputum sample using a special microscope.

If coughing does not produce sputum, a breathing treatment may be given before the test to trigger sputum production.

There is no discomfort.