Sputum direct fluorescent antibody (DFA)
Alternative Names: Direct immunofluorescence test; Direct fluorescent antibody - sputum
Sputum direct fluorescent antibody (DFA) is a test that looks for microorganisms in lung secretions.
Why is the Test Performed?
Your doctor may order this test if you have signs of certain lung infections or pneumonias.
How is the Test Performed?
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 "tagged." 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.
Preparation for the Test
If coughing does not produce sputum, a breathing treatment may be given before the test to trigger sputum production.
How will the Test Feel?
There is no discomfort.
Sputum direct fluorescent antibody (DFA) Risks
There are no risks.
Normal Results for Sputum direct fluorescent antibody (DFA)
Normally, there is no antigen-antibody reaction.
What Abnormal Results Mean
Abnormal results may be due to an infection such as Legionnaire's disease, mycoplasma pneumonia , or chlamydia pneumonia.
Learn more about Sputum direct fluorescent antibody (DFA)
Reviewed 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.
Copyright 2011 A.D.A.M., Inc.
