Sputum direct fluorescent antibody (DFA)
Direct immunofluorescence test; Direct fluorescent antibody - sputum
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 micro-organisms are 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:
- Legionnaire disease
- Pneumonia due to certain bacteria, viruses, fungi, or other micro-organisms
Risks
There are no risks with this test.
References
Banaei N, Deresinski SC, Pinsky BA. Microbiologic diagnosis of lung infection. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 19.
Patel R. The clinician and the microbiology laboratory: test ordering, specimen collection, and result interpretation. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 16.
Version Info
Last reviewed on: 4/29/2022
Reviewed by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
