Evaluation of BioPlex 2200 syphilis IgG for the diagnosis of syphilis

Objectives: The serological detection of specific antibodies to Treponema pallidum is of particular importance in the diagnosis of syphilis. The purpose of this study was to evaluate diagnostic performances of BioPlex 2200 Syphilis (BioRad), an innovative test based on MFI technology (Multiplex Flow Immunoassay), in comparison with ARCHITECT Syphilis TP (Abbott). As confirmatory tests, TPHA and Western Blot (WB) were used. Methods: Study group. A retrospective study was performed with 553 samples. In particular we studied 200 specimens from syphilis patients of various disease stages, 200 unselected samples submitted to the Microbiology Laboratory of the St. Orsola Hospital in Bologna for routine serological lue screening, 100 samples from blood donors and 53 samples reactive by ARCHITECT, but negative by both TPHA and WB. BioPlex 2200 Syphilis IgG. BioPlex Syphilis IgG kit uses three different sets of beads coated with recombinant proteins from T. pallidum (15 KDa, 17 KDa, and 47 KDa). After the reaction mixture is incubated and washed, a phycoerythrin conjugated reporter antibody is added to the reaction mixture. Following a second incubation and wash cycle, the beads are suspended in buffer and passed through a flow-based detector. The results have been classified as negative (1.1). ARCHITECT Syphilis TP. ARCHITECT Syphilis TP is a two-step immunoassay for the qualitative detection of IgG and/or IgM to T. pallidum in human serum or plasma using chemiluminescent microparticle immunoassay (CMIA) technology. Confirmatory methods. Commercial tests were used for TPHA and RPR (Randox). Titres >= 80 were considered as positive for TPHA testing. A home-made WB was used and an IgG test was considered positive when at least three out of the four following T. pallidum antigens were present: Tp15, Tp17, TmpA and Tp47. Results: Considering WB as the gold standard, the sensitivity and specificity of Bioplex 2200 Syphilis IgG were 100% and 93.2%, respectively, whereas the agreement was 95.7%. When compared to WB, sensitivity and specificity of Architect Syphilis were 100% and 84.9%, respectively, being the agreement 90.4%. Conclusions: BioPlex 2200 Syphilis IgG test showed to be a very sensitive and specific method for the laboratory diagnosis of syphilis. Because of its performances, and Bioplex system high throughput and walk-away capability, this assay can be considered an excellent alternative to the traditional test