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Sputum direct fluorescent antibody (DFA) test

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

  • Alternative Names
    • Direct immunofluorescence test; Direct fluorescent antibody - sputum

  • 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
  • Risks
    • There are no risks with this test.

  • 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.