Background/introduction UK syphilis incidence is rising. There are no national data on neurosyphilis prevalence. The CDC defines confirmed neurosyphilis as positive CSF VDRL at any syphilis stage and presumptive neurosyphilis as non-reactive CSF VDRL, raised CSF protein or WCC, positive serum VDRL and clinical symptoms/signs of neurosyphilis in the absence of any other causes. VDRL and RPR perform the same function; however, sensitivity of VDRL in CSF is poor (30–70%) and RPR even poorer.

Aim(s)/objectives To identify and characterise patients referred and treated for neurosyphilis in a London HIV/GUM service.

Methods We reviewed all cases referred for investigation of possible neurosyphilis September 2012–September 2014.

Results 1615 new diagnoses of syphilis were identified. 34 were referred for suggestive symptoms. 24(71%) were treated although only 6(25%) met CDC criteria for confirmed or presumptive neurosyphilis. Of those treated, 67% were HIV+, 4 had positive RPR (2 had no other CSF abnormality), 10 had positive TPPA only and 3 had no CSF abnormality.

Discussion/conclusion No single laboratory test is both sensitive and specific making diagnosis challenging. CSF interpretation may be particularly difficult in HIV+ individuals as HIV itself can cause pleocytosis and elevated protein concentrations. Conversely, Marra et al . showed that in 32% of HIV+ patients with neurosyphilis, the only CSF abnormality was a positive VDRL. We suggest that given the poor sensitivity of CSF RPR, and that CSF may be normal in neurosyphilis, most decisions to treat for neurosyphilis should be based on clinical symptoms/signs rather than CSF findings.