What is the confirmatory test for syphilis?

The confirmatory test for syphilis is the FTA-ABS (Fluorescent Treponemal Antibodies Absorption) test. This test is highly specific for Treponema pallidum, the bacterium that causes syphilis. It detects antibodies that are produced in response to an infection with treponemes, ensuring that a positive result is specific to syphilis rather than cross-reacting with other conditions.

The FTA-ABS is used after initial screening tests, such as the RPR (Rapid Plasma Reagin) or VDRL (Venereal Disease Research Laboratory) tests, which are non-treponemal tests. These initial tests may yield false positives due to various factors, leading to the need for a more specific confirmatory test.

While the RPR and VDRL are valuable for initial screening and monitoring of treatment efficacy, they are not definitive for diagnosing syphilis because they can also indicate other medical conditions that may cause elevated non-treponemal antibodies. ELISA (Enzyme-Linked Immunosorbent Assay) can also be used as a screening test for syphilis, but again, it may not be as specific as the FTA-ABS