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Sputum direct fluorescent antibody (DFA)
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Sputum direct fluorescent antibody (DFA)

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Direct immunofluorescence test; Direct fluorescent antibody - sputum

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

I Would Like to Learn About:

  • 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.

Related Information

  Legionnaire diseas...Mycoplasma pneumon...     Pneumonia

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.

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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.

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