Evaluation of recomWell Treponema, a novel recombinant antigen-based enzyme-linked immunosorbent assay for the diagnosis of syphilis

Objective. To evaluate the diagnostic performance of an enzyme immunosorbent assay (recomWell Treponema) for the diagnosis of syphilis. The novel recombinant antigens Tpn47, TpN17 and TpN15 were utilized. Methods. A total of 782 human serum specimens, belonging to four different categories (blood donors, n = 200; routine laboratory screening for syphilis, n = 400; syphilis patients, n = 122; potential cross-reactors, n = 60), were evaluated to compare the sensitivity and specificity of the recomWell Treponema kit with a standard whole Treponema pallidum cell lysate antigen-based ELISA (Syphilis Screening) and with microhaemagglutination (MHA-TP). Results. The overall specificity and sensitivity of the recomWell Treponema IgG was 98.9% and 98.3%, respectively. The specificity and sensitivity of Syphilis Screening ELISA was 98.7% and 98.3%, respectively. The agreement between recomWell Treponema and Syphilis Screening was 100%, 97.8%, 95.9% and 95% among the blood donor specimens, screening samples, syphilis specimens and the potential cross-reactors, respectively. Values of concordance varying from 96.7% to 98.3% were found in the different groups of sera between recomWell Treponema and MHA-TP. In addition, recomWell Treponema demonstrated a good diagnostic performance when used to detect the IgM to T. pallidum. No false-positive sera were identified and. in 17/19 samples from primary infection, an IgM immune response was found. Conclusions. recomWell Treponema was shown to be a highly specific and sensitive method in all stages of syphilis screening and it can be considered as alternative to other ELISA tests based on native antigen preparations.