Evaluation of the BioPlex 2200 Syphilis System as a First-Line Method of Reverse-Sequence Screening for Syphilis Diagnosis

Despite recent technologic advances, the diagnosis of syphilis remains a challenging enterprise. Actually, most high-volume laboratories have adopted the "reverse algorithm" due several factors, including the potential to automate testing. Recently, immunoassays processed on random-access systems have been proposed as screening tests. The purpose of this study was to evaluate diagnostic performances of BioPlex® 2200 Syphilis IgG and BioPlex® 2200 Syphilis IgM, tests based on Multiplex Flow technology, in comparison with ARCHITECT® Syphilis TP, a chemiluminescent immunoassay for the detection of IgG and/or IgM anti-Treponema pallidum.A retrospective study was performed with a panel of 100 blood donors sera, a panel of 350 clinical and laboratory characterized syphilitic sera and 170 samples obtained from subjects with potentially interfering conditions. Moreover, 200 unselected samples submitted to the Microbiology Laboratory of St. Orsola Hospital in Bologna for routine screening for syphilis were evaluated. As confirmatory tests, T. pallidum haemagglutination and Western Blot were used.Considering IgG WB as the gold standard method, BioPlex® 2200 Syphilis IgG specificity was far higher than ARCHITECT® Syphilis TP: 89.7% and 78.4%, respectively, whereas the sensitivity was 100% for both automated methods. Compared to IgM WB BioPlex® 2200 Syphilis IgM performed with a specificity of 94.9%, whereas the sensitivity was 84.8%. Considering the excellent easy of use and automation, the high samples throughput and its valuable analitical performances, BioPlex® Syphilis 2200 IgG could represent a suitable choice for high-volume laboratories. BioPlex® Syphilis 2200 IgM could be considered a good addition to IgG testing for uncovering active infections.