MedlinePlus Medical Encyclopedia: Sputum direct fluorescent antibody (DFA)

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Sputum direct fluorescent antibody (DFA)

Contents of this page:
Alternative Names Definition How the Test is Performed How to Prepare for the Test How the Test Will Feel	Why the Test is Performed Normal Results What Abnormal Results Mean Risks

Alternative Names

Direct 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. Such 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 by use of 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: 5/29/2007

Updated by: Daniel R Alexander, MD, Department of Internal Medicine, St. Mary's Hospital, Leonardtown, MD. Review provided by VeriMed Healthcare Network.

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