Evaluation of Treponemal Tests for Improved Diagnosis of Neurosyphilis

Background: The diagnosis of neurosyphilis remains a challenge. The VDRL-CSF test which has been the mainstay for laboratory diagnosis is very specific but lacks sensitivity. Treponemal-specific serum tests used for cerebrospinal fluid (CSF) testing could aid in the diagnosis.

Methods: A total of 32 patients including 18 controls who were seen at Emory Healthcare in Atlanta were enrolled in the study. Thirty patients had a variety of neurologic signs and symptoms while two patients had positive VDRL-CSF (one was asymptomatic, the second was a referred sample with no history). CSF samples were tested with the Trep-Sure and Maxi-Syph EIAs, INNO-LIA, and TP-PA serological tests. PCR testing targeted the polA gene of T. pallidum. There was insufficient CSF for all samples to be tested with all tests. To calculate sensitivity and specificity of the tests, neurosyphilis was defined as patients whose CSF tested positive by at least 2 treponemal tests even if the VDRL-CSF was non-reactive.

Results: Fourteen patients were diagnosed with neurosyphilis based on having at least 2 tests positive; 12 were symptomatic, one was asymptomatic, and one had no history. The 18 patients in the control group had neurologic symptoms. VDRL-CSF had a sensitivity of 85.7% (12/14) and a specificity of 100%. 13 of the 14 patients tested positive by Trep-Sure EIA (sensitivity 92.3%, specificity 100%). TP-PA had a sensitivity of 83.3% (10/12) and a specificity of 100% and INNO-LIA had a sensitivity of 92.3% and specificity of 100% (12/13). Maxi-Syph EIA had a sensitivity and specificity of 100% (10/10). PCR for T. pallidum was positive in 3 CSF specimens from patients classified as having neurosyphilis.

Conclusions: The Trep-Sure EIA, Maxi-Syph EIA and INNO-LIA were useful in identifying two symptomatic patients with non-reactive VDRL-CSF and to confirm those with reactive VDRL-CSF test.