Treponema pallidum surface immunofluorescence assay for serologic diagnosis of syphilis

A surface immunofluorescence assay (SIFA) using live spirochetes was analyz ed and compared with Western blot (WB), fluorescent. treponemal antibody ab sorption (FTA-ABS), microhemagglutination (MHA-TP), and Treponema pallidum immobilization (TPI) assays for detecting serum antibodies to T. pallidum i n patients with syphilis, in disease controls, and in healthy subjects. SIF A and WE were 99% sensitive (99 of 100 positive specimens) and specific (14 0 of 140 negative specimens); FTA-ABS showed a sensitivity and a specificit y of 90 and 89% (90 of 100 positive and 125 of 140 negative specimens), res pectively. MHA-TP showed a sensitivity of 84% (84 of 100 positive specimens ) and a specificity of 98.5% (138 of 130 negative specimens). Finally, TPI had a sensitivity of 52% (52 of 100 positive specimens) and a specificity o f 100% (140 of 140 negative specimens). The T, pallidum SIFA was therefore highly specific, showing no equivocal reactivities with control sera, and s ensitive, The results suggest the possible use of SIFA as a confirmatory te st in the serologic diagnosis of syphilis.