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Alternative NamesDirect immunofluorescence test; Direct fluorescent antibody - sputum
Definition Return to top
Sputum direct fluorescent antibody (DFA) is a test that looks for microorganisms in lung secretions.
How the Test is Performed Return to top
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.
How to Prepare for the Test Return to top
If coughing does not produce sputum, a breathing treatment may be given before the test to trigger sputum production.
How the Test Will Feel Return to top
There is no discomfort.
Why the Test is Performed Return to top
Your doctor may order this test if you have signs of certain lung infections or pneumonias.
Normal Results Return to top
Normally, there is no antigen-antibody reaction.
What Abnormal Results Mean Return to top
Abnormal results may be due to an infection, such as Legionnaire's disease or mycoplasmal pneumonia.
Risks Return to top
There are no risks.Update Date: 8/8/2008 Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.