Confirming Syphilis Diagnosis

Definitive Diagnostic Methods

The Centers for Disease Control and Prevention recommends darkfield microscopy and direct fluorescent antibody (DFA) testing of lesion exudate or tissue as the definitive methods for diagnosing early syphilis when lesions are present 1
Direct detection methods provide immediate confirmation of Treponema pallidum infection without waiting for antibody development 1
Darkfield examination should be performed on suspicious lesions or body fluids, such as nasal discharge in congenital syphilis 4

The Centers for Disease Control and Prevention recommends that nontreponemal tests (VDRL or RPR) must be performed quantitatively and reported with titers 1
Treponemal tests (FTA-ABS or TP-PA) are used for confirmation 1
A fourfold change in titer represents a clinically significant difference 1

In primary syphilis, darkfield microscopy or DFA testing of the chancre provides immediate diagnosis 1
In secondary syphilis, both nontreponemal and treponemal tests are highly sensitive (97-100%) 3
In latent syphilis, nontreponemal test sensitivity decreases in late latent disease (61-75%) 2

For HIV-infected patients, CSF examination is recommended for all persons with late-latent syphilis or syphilis of unknown duration 5
For pregnant women, maternal serum testing is preferred over umbilical cord blood 4
For congenital syphilis, quantitative nontreponemal test (RPR or VDRL) must be performed on infant serum, not cord blood 4

Never use only one type of serologic test for diagnosis, as recommended by the Centers for Disease Control and Prevention 1
Never compare titers between different test types (VDRL vs. RPR) 2
Never use treponemal test titers to assess treatment response or disease activity 2