Serodiagnosis of syphilis by an enzyme-linked immunosorbent assay for IgG antibodies against the Reiter treponeme flagellum.

An enzyme-linked immunosorbent assay for IgG antibodies against the flagellum (axial filament) of the Reiter treponeme (flagellum-ELISA) was developed and compared with the fluorescent treponemal antibody absorption (FTA-ABS) test and the Treponema pallidum immobilization (TPI) test with regard to diagnostic sensitivity and specificity. One serum from each of 827 individuals with and without syphilis was studied. In all diagnostic groups of syphilis there was no significant difference between the sensitivity of the FTA-ABS and the flagellum-ELISA, except in treated syphilis, where the FTA-ABS was more sensitive (P less than 0.01). In primary syphilis and in treated syphilis the sensitivity of the flagellum-ELISA was higher than the sensitivity of TPI (P less than 0.01 and P less than or equal to 0.05), respectively); in all other groups there was no significant difference between the sensitivity of TPI and flagellum-ELISA. The specificity of the flagellum-ELISA (99.0%) in 200 sera from blood donors without syphilis was not statistically different from the specificity of FTA-ABS (98.0%) and TPI (99.5%). The flagellum-ELISA seems to be well suited for routine serodiagnosis of syphilis and may replace other treponemal tests.