Treponema pallidum apparently invades the CNS in 40% of patients with syphilis. With time there have been changing guidelines as to what is the serum RPR or TPHA titres that indicate the need for lumbar puncture to be done in patients who are asymptomatic. What is the current consensus given the resurgence of the disease?
These include dark-field microscopy, PCR, and direct fluorescent antibody testing for T pallidum. In some cases, these tests may allow the diagnosis of syphilis prior to a serologic response.
There are 2 different types of serologic tests classified based on the type of antigen the antibodies are directed against. Treponemal tests detect antibody to T pallidum proteins. Nontreponemal tests detect antibodies directed against lipoidal antigens, damaged host cells, and possibly from treponemes.