Sputum DFA (direct fluorescent antibody)

Definition

Sputum DFA is a test performed to detect the presence of microorganisms in sputum (lung secretions) by using antibodies tagged with a fluorescent dye.

How the test is performed

A sputum sample is obtained by coughing into a specimen container. In the laboratory, antibodies that have been chemically linked to a fluorescent dye are added to the sample. The flagged antibodies will attach themselves to the specific antigens (in this case, the microorganism against which they were formed). The specific microorganism (antigen) is indirectly identified by the presence of fluorescence when examined under a special microscope.

How to prepare for the test

Obtain a coughed sputum specimen. If there is not a productive cough, a respiratory treatment may produce a sample.

How the test will feel

There is no discomfort.

Why the test is performed

This test may be performed when certain types of pulmonary infections or pneumonias are suspected.

Normal Values

Normally, there is no antigen-antibody reaction. A reaction indicates infection.

What abnormal results mean

Abnormal results may indicate a specific infection depending on the antigens tested. Legionnaire's disease or mycoplasmal pneumonia are 2 infections that can be determined by this test.

What the risks are

There are no risks.

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Direct immunofluorescence test