Fluorescence Treponema Antibody Absorption Test

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The fluorescence treponema antibody absorption test (abbreviated: FTA-Abs test ) is a diagnostic detection method in serology for an infection with Treponema pallidum , the causative agent of syphilis (syphilis). Similar to the Treponema Pallidum Hemagglutination Assay (TPHA), antibodies are detected from patient serum .

execution

The test is carried out to detect specific antibodies against antigens of the pathogenic ( disease-causing ) bacterium Treponema pallidum.

However, since apathogenic Treponema species can also occur in the normal flora of the oral cavity, against whose antigens the body has then formed antibodies, which also deliver a (then false) positive test result, these antibodies must be removed from the patient sample before the actual test - absorbed - to be. For this purpose, the patient's blood serum is first incubated with antigens of a non-pathogenic Treponema species (so-called Reiter spirochetes) so that existing antibodies bind to their antigens. Only then is the serum sample prepared in this way applied to a slide on which there are fixed antigen structures of Treponema pallidum (so-called Nichols strain , preserved from the brain of a syphilitic person) and then incubated again. Afterwards, all unbound material is removed by washing processes. Now this slide is covered with special antibodies which are marked with a fluorescent dye and are directed against the (in the case to be detected) already bound human antibodies.

If there are antibodies against the Treponema pallidum antigens in the serum, they will stick to the slide after the washing process and can be detected under a fluorescence microscope using the fluorescently labeled anti-antibodies .

There is both a qualitative and a quantitative FTA-Abs test.

This procedure is necessary to confirm a positive result of the TPHA test.

The phase of the illness (e.g. acute or latent) must be determined with a complement fixation reaction (CFR) and possibly a special IgM FTA Abs.

literature

• Medical microbiology . 3. Edition. Thieme-Verlag, p. 427

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