Serological evaluation of antigen Tp0693 for diagnosis of syphilis.

The aim of the present study was to evaluate the diagnostic value of the Treponema pallidum (Tp) antigen Tp0693 for syphilis. ELISA was used to examine the serum levels of Tp0693. The sample-to-cutoff ratio (S/CO) value was used to generate a receiver operating characteristic (ROC) curve. A correlation analysis was performed to compare the detection efficacy of Tp0693-specific ELISA, Treponema pallidum Particle Agglutination (TPPA), Tolulized Red Unheated Serum test (TRUST) and LiZhu™ Tp-ELISA. The area under the ROC curve was 0.99, indicating good diagnostic efficacy. When the diagnostic specificity reached 100%, the diagnostic sensitivity was up to 93.5%. Tp0693-specific ELISA results were not correlated with those of TPPA, TRUST and LiZhu™ Tp-ELISA (correlation coefficient, 0.122, 0.114 and 0.025, respectively). The latent syphilis rate was highest (12%, 9/75) for all syphilis specimens with a S/CO in the grey area. In conclusion, for syphilis specimens with a S/CO in the grey area, TPPA should be used for further confirmation of the diagnosis. Tp0693 may be used as a diagnostic antigen for syphilis; however, further study regarding its potential use is required.