Which sequence best describes the diagnostic approach for primary syphilis?

Which sequence best describes the diagnostic approach for primary syphilis?

• A. Darkfield microscopy; Screening Tests: RPR, VDRL; Confirmatory test: FTA-ABS
• B. RPR; VDRL; FTA-ABS; Darkfield
• C. Darkfield microscopy; Confirmatory test: FTA-ABS; Screening Tests: RPR, VDRL
• D. FTA-ABS; Darkfield microscopy; RPR

Answer: (A)

In primary syphilis, the diagnostic approach combines direct visualization with serologic testing. Darkfield microscopy can directly show Treponema pallidum from a chancre, providing rapid, organism-level evidence when a lesion is present. Because darkfield requires special technique and isn’t always available, serologic testing is the routine backbone: start with a non-treponemal screening test such as RPR or VDRL, which detects antibodies produced in response to infection. If that screening test is positive, confirm the diagnosis with a treponemal test like FTA-ABS. This sequence—darkfield when feasible, followed by screening serology and then treponemal confirmation—best reflects how clinicians integrate direct detection with widely available serology to establish a diagnosis.

In primary syphilis, the diagnostic approach combines direct visualization with serologic testing. Darkfield microscopy can directly show Treponema pallidum from a chancre, providing rapid, organism-level evidence when a lesion is present. Because darkfield requires special technique and isn’t always available, serologic testing is the routine backbone: start with a non-treponemal screening test such as RPR or VDRL, which detects antibodies produced in response to infection. If that screening test is positive, confirm the diagnosis with a treponemal test like FTA-ABS. This sequence—darkfield when feasible, followed by screening serology and then treponemal confirmation—best reflects how clinicians integrate direct detection with widely available serology to establish a diagnosis.