Analysis of Bioplex Syphilis IgG Quantitative Results in Different Patient Populations

Because of the need to reduce labor costs, many laboratories are replacing the traditional syphilis testing algorithm—screen-ing with a manual nontreponemal test, followed by an anti-Treponema pallidum antibody test—with a “reverse ” algorithm that uses an automated immunoassay to screen for anti-T. pallidum IgG antibodies. A rapid plasma reagin (RPR) titer determination is then performed on IgG-reactive specimens to (i) verify syphilis by an alternative method and (ii) obtain a titer for patient management. In addition, some laboratories also perform a traditional treponemal assay (fluorescent trepo-nemal antibody absorbed [FTA-ABS] or T. pallidum particle agglutination [TP-PA] assay) on specimens that test positive by an IgG screening assay. A number of studies have shown that anti-T. pallidum IgG immunoassays have sensitivities and spec-ificities that are comparable to those of other treponemal as-