Background The laboratory diagnosis of syphilis is a crucial point in the diagnostic evaluation of the syphilis. The aim of this study was to evaluate the diagnostic performance of the new commercial immunoblotting “recomLine Treponema” (Mikrogen Diagnostik, Germany) assay which includes two new recombinant antigens (Tp257 (Gpd) and Tp453) in addition to the four (Tp47, TmpA, Tp17, Tp15) shown in a previous version.

Methods The presence of specific antibody response to T. pallidum was evaluated by comparing the immunoblotting test, that detects both IgG and IgM antibodies, with the “Syphilis TP“ (Architect system, Germany) immunoassay, that detects the total T. pallidum specific antibody and routinely used in our Hospital for serological screening. The serum samples included in this study were obtained from 112 patients with suspect or clinical evidence of syphilis infection.

Results Of the 112 samples analysed for specific T. pallidum antibody by “Syphilis TP” assay, 90 samples were detected positive, 8 negative, 10 borderline and 4 samples showed an not interpretable result.

Of the 112 samples analysed for specific IgG and IgM antibodies by “recomLine Treponema” assay, 97 (86.61%) specimens resulted positive (100% were IgG positive and 16.49% were also IgM positive), 7 (6.25%) negative and 8 (7.14%) borderline (6 for the IgG and 2 for the IgM).

Conclusion The comparison between the two test showed that the “recomLine Treponema” assay identified more positive sample, less negative and borderline samples and not interpretable results.

This preliminary results underline that the “recomLine Treponema” (Mikrogen Diagnostik, Germany) test is clinically valid not only because it can be used as confirmatory test but also because it allows to discriminate between IgG and IgM antibodies.

Future objectives of this study will be to validate the “recomLine Treponema” test on other groups of subjects and compare it with other serological tests.