Background In the past decade, China has observed an annual increasing rate of syphilis over 14% and the cases of neurosyphilis were increased accordingly. The WHO standard method for screening neurosyphilis is examination of CSF fluid and a mandatory VDRL laboratory procedure. The situation is even more challenging in China as there are no commercial VDRL reagents approved by the SFDA for CSF-VDRL examination. In this study we aimed to determine the performance characteristics of CSF-TRUST as compared to CSF-VDRL for laboratory diagnosis of neurosyphilis.

Methods CSF and serum samples were collected from 824 individual STD clinic patients who have syphilis and are suspected to progress to neurosyphilis in a 9-month period. CSF-VDRL and CSF-TRUST were performed in parallel on the same day when collected. TPPA tests were also performed on the CSF and the serum samples, and Biochemical analysis of the CSF samples was also performed.

Results The overall agreement between CSF-TRUST and CSF-VDRL was 97.3%. The reactive ratios of the CSF samples were 22.1% by CSF-TRUST and 24.8% by CSF-VDRL, respectively. All CSF-TRUST reactive cases were reactive in the CSF-VDRL. Twenty-two samples with CSF-TRUST negative were tested CSF-VDRL reactive with low titers (1:1 to 1:4). Over 97% of the double reactive CSF samples (CSF-VDRL and CSF-TRUST) had an identical titer or a titer within a 2-fold difference. The agreement of CSF-TPPA and CSF-VDRL was 71.9%. Similarly the agreement of CSF-TPPA and CSF-TRUST was 69.2%.

Conclusions TRUST reagent kit is commercially available in China with SFDA certificate. It seems that CSF-TRUST and CSF-VDRL are congruence in most cases, but CSF-TRUST is less sensitive than CSF-VDRL. Nevertheless, our results suggested that CSF-TRUST may be used as an alternative for laboratory diagnosis of neurosyphilis in clinical settings with CSF-VDRL unavailable.