What is the role of lab testing in the diagnosis of neurosyphilis?

Updated: Jul 17, 2018
  • Author: Richard P Knudsen, MD, FAAN, FAAP; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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No laboratory study has proven sufficiently sensitive or specific to serve as a single test for the definitive diagnosis of neurosyphilis. The diagnosis of syphilis has remained more difficult than the diagnosis of most other infections. The organism has not been successfully grown in culture, so diagnosis relies on evidence of immunologic response to infection or to visualization of the organism from an active chancre or condyloma.

Dark-field microscopy of the skin lesions is the most specific technique for diagnosis. This requires the presence of live treponemes from serous exudates collected gently on a glass slide. Microscopically, the spirochete has a characteristic corkscrew appearance.

Biopsy with direct fluorescent antibody staining of material from the lesion has been successful. Further, the recently completed sequencing of the genome for Treponema pallidum may offer improved diagnostic testing; currently, however, serologic testing is the standard.

Again, no single laboratory test is both sensitive and specific to the diagnosis of neurosyphilis. Many major clinical guidelines suggest that negative CSF treponemal-specific antibody tests rule out the diagnosis of neurosyphilis, but the Hopkins group realized that a negative test may not exclude the diagnosis if the clinical suspicion is high. [45]

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