Neurosyphilis is unlikely in patients with late latent syphilis and a negative blood VDRL-test.

Patients with latent syphilis or syphilis of unknown duration should be evaluated for tertiary disease and neurosyphilis. The aim of this retrospective study was to determine relevant serological parameters for the identification of those individuals with syphilis who are most likely to have neurosyphilis and who therefore require lumbar puncture. After excluding repeated estimates and patients whose blood syphilis serology had either been negative or not been determined within 3 months of lumbar puncture, 265 out of 710 cerebrospinal fluids from 1988 to 2004 were analysed. In each of those patients the earliest available pairs of serum and cerebrospinal fluid samples were evaluated. The diagnosis of neurosyphilis was based on criteria according to established guidelines. Forty-three of 265 patients (16.2%; 5 women, 38 men; mean age 47+/-16 years) had neurosyphilis. Seven of 72 (9.7%) of those testing HIV-positive, fulfilled the criteria of neurosyphilis. Not a single patient with neurosyphilis tested Venereal Disease Research Laboratory test (VDRL)-negative in peripheral blood, an effect which was highly significant (p < 0.01, chi2-test). The median blood-VDRL titre was significantly higher in patients with neurosyphilis than in those without (1:32 vs. 1:0; p < 0.01, t-test, two-sided). Hence, neurosyphilis is very unlikely in patients with a negative blood-VDRL. Therefore, lumbar puncture is not recommended in these patients.