Syphilis - Dx

The fact that treponema pallidum cannot be cultured presents diagnostic challenges, as we must rely on serologic tests.

a) Non-treponemal tests: test for antibodies against an antigen non-specific for syphilis (RPR, VDRL) - sensitive, thus used to rule out infection

b) Treponemal tests: test for antibodies against treponemal antigens - specific, thus used as confirmatory tests

c) Neurosyphilis

      - In pts with an unknown syphilis history, the above screening tests apply and can rule out neurosyphilis

      - In pts with known syphilis, indications for LP are high titers (>1:32) or HIV coinfection

         - CSF VDRL is only 30% sensitive for neurosyphilis

         - CSF abnormalities can be mild, with lymphocytes >5 cells/microL and protein >45 mg/dL consistent with the diagnosis

      - Once therapy is initiated, serial LPs are indicated to evaluate for treatment efficacy

      - VDRL titers and WBC/protein should normalize within two years

(Christopher Woo MD, 7/20/10)