1408. Treponema pallidum-Specific Antibody Testing in the Evaluation of Neurosyphilis, a Prospective Trial

Background The therapeutic challenges of neurosyphilis are rooted in its diagnosis and management, with potential for complications arising from asymptomatic, unrecognized, or under-treated disease. Currently, the non-treponemal VDRL testing of cerebrospinal fluid (CSF) samples is used to predict those with CNS invasion by T. pallidum. However, more extensive evaluation of those at any stage of infection demonstrates both that the incidence of CNS invasion is much greater than predicted, and there exists a large proportion of false positives from VDRL testing alone. Methods Subjects with suspected neurosyphilis were recruited from the infectious disease clinic after referral to LAC+USC Hospital. Informed consent was obtained and subjects underwent clinical examination, including a standardized neurological and neurocognitive evaluation and CSF sampling. A CSF-specific VDRL, FTAabs, and a T. pallidum particle agglutination index were calculated: A TPPA Index >2.0 was defined as positive and definitive evidence of neurosyphilis Results 40 subjects were recruited, 8 were HIV-negative and 32 HIV positive, of which, 1 declined to continue after CSF sampling (Table 1). Employing the CSF TPPA index, 7/31 HIV positive (22.6%) and 1/8 HIV-negative individuals (12.5%) had neurosyphilis (Table 2). Discordant results with the CSF VDRL were common; 4/31 subjects (12.9%) with a positive CSF VDRL had a TPPA Index < 2.0 (0.227, 0.227, 0.315, and 0.400) and 4/31 subjects (12.9%) with a negative CSF VDRL had a positive TPPA index (2.234, 3.333, 3.797, and 4.548, Table 3). Neurocognitive and neurologic abnormalities were commonly encountered in this population both with and without documented neurosyphilis. Conclusion Our investigations demonstrate the value of CSF sampling in persons with any stage of syphilis and establish the utility of T. pallidum-specific antibody testing to greatly facilitate clinical decision-making. The diagnostic tools to evaluate the T. pallidum-specific immunological response of the CNS to syphilis are currently widely available, inexpensive, but woefully underutilized Disclosures All authors: No reported disclosures.