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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. (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 Results:

Normally, there is no antigen-antibody reaction.

What Abnormal Results Mean:

Abnormal results may be due to an infection such as Legionnaire disease, mycoplasma pneumonia, or chlamydia pneumonia.

Risks:

There are no risks.

References:

Croft AC, Woods GL. Specimen collection and handling for diagnosis of infectious diseases. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 63.

Pitt BS, Yao JDC. Microbiologic diagnosis of lower respiratory tract infection. In: Mason RJ, Murray JF, Broaddus VC, et al., eds. Murray and Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, PA: Elsevier Saunders; 2010:chap 18.


Review Date: 5/29/2014
Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician 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. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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