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Sputum direct fluorescent antibody (DFA)

Definition:

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



Alternative Names:

Direct immunofluorescence test; Direct fluorescent antibody - sputum



How the test is 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.



How to prepare for the test:

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



How the test will feel:

There is no discomfort.



Why the test is performed:

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



Normal Values:

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.



What the risks are:

There are no risks.



Special considerations:



References:

Limper AH. Overview of pneumonia. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 97.




Review Date: 5/28/2012
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. Health Solutions, Ebix, Inc.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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