Laboratory investigation of syphilis.

Without treatment, syphilis passes through primary, secondary, latent, and tertiary stages. The disease can be diagnosed directly by microscopic identification of the infective organism or serologically. Nontreponemal serologic tests are most suitable for screening and following response to therapy, while treponemal tests are used to confirm a positive nontreponemal test result. Biologic false positives are not uncommon. Because of the danger of infection to the fetus, serologic testing for syphilis is mandatory in all pregnant women. Nontreponemal tests can also be performed on CSF to document neurosyphilis.