Comparison of intrathecal synthesis of Treponema pallidum-specific IgG antibodies and polymerase chain reaction for the diagnosis of neurosyphilis.

An indirect Treponema pallidum-IgG enzyme-linked immunosorbent assay (Tp-IgG-ELISA) was used for the estimation of intrathecal synthesis of specific IgG antibodies in patients with syphilis. Detection of T. pallidum DNA in cerebrospinal fluid (CSF) samples of syphilitic patients was performed by amplification of treponemal DNA, using the polymerase chain reaction (PCR). Both methods were compared as to their suitability for diagnosis of neurosyphilis in 37 patients with syphilis. Intrathecal synthesis of T. pallidum-specific IgG and PCR was negative in 16 patients with treated syphilis or untreated secondary syphilis. In contrast, an intrathecal IgG antibody production was found in all 21 patients with treated or untreated neurosyphilis. PCR was only positive in CSF samples from six out of ten patients with untreated neurosyphilis. The findings suggest that the intrathecal production of T. pallidum-specific IgG antibodies is an important indicator for the diagnosis of neurosyphilis. In addition, a positive result by PCR performed in CSF establishes a diagnosis of active neurosyphilis.