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Sputum direct fluorescent antibody (DFA) test

Sputum direct fluorescent antibody (DFA) is a lab test that looks for micro-organisms in lung secretions.

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.)

The sample is sent to a lab. There, a fluorescent dye is added to the sample. If the micro-organism 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 with this test.

Why the Test is Performed

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

Normal Results

Normally, there is no antigen-antibody reaction.

What Abnormal Results Mean

Abnormal results may be due to an infection such as:

Risks

There are no risks with this test.

Alternative Names

Direct immunofluorescence test; Direct fluorescent antibody - sputum

References

Banaei N, Deresinski SC, Pinsky BA. Microbiologic diagnosis of lung infection. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 17.

Murray PR. The clinician and the microbiology laboratory. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 16.

Review Date 5/20/2016

Updated by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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