Which test is confirmatory for syphilis?

Which test is confirmatory for syphilis?

• A. Darkfield microscopy
• B. RPR
• C. VDRL
• D. FTA-ABS

Answer: (D)

Confirming syphilis relies on detecting antibodies that specifically target Treponema pallidum. The test that best serves as a confirmatory assay is the FTA-ABS, which uses fluorescent-labeled anti-human antibodies to detect anti-treponemal antibodies in the patient’s serum. It has high specificity and typically remains positive after infection, making it reliable to confirm true syphilis following a positive initial screen. Non-treponemal tests like the screening ones measure antibodies to cardiolipin and are useful for screening and monitoring treatment response, but they aren’t specific to Treponema pallidum and can yield false positives or be affected by other conditions, so they aren’t definitive for confirmation. Darkfield microscopy can visualize live spirochetes from lesions and is helpful in early primary syphilis, but it is technically demanding and not used as a standard confirmatory test.

Confirming syphilis relies on detecting antibodies that specifically target Treponema pallidum. The test that best serves as a confirmatory assay is the FTA-ABS, which uses fluorescent-labeled anti-human antibodies to detect anti-treponemal antibodies in the patient’s serum. It has high specificity and typically remains positive after infection, making it reliable to confirm true syphilis following a positive initial screen.

Non-treponemal tests like the screening ones measure antibodies to cardiolipin and are useful for screening and monitoring treatment response, but they aren’t specific to Treponema pallidum and can yield false positives or be affected by other conditions, so they aren’t definitive for confirmation. Darkfield microscopy can visualize live spirochetes from lesions and is helpful in early primary syphilis, but it is technically demanding and not used as a standard confirmatory test.