Solid-phase hemadsorption assay for IgM antibody to Treponema pallidum in serum and umbilical cord blood

A solid-phase hemadsorption assay (SPHA) for Treponema pallidum was evaluated using serum and umbilical cord blood. A total of 133 sera reactive using immunofluorescent antibody assay were tested by SPHA for IgM antibody against T. pallidum. They were categorized into clinical stages of syphilis, including eight sera with primary, 32 sera with secondary, 68 sera with latent, 21 sera with unclassified, and four sera with congenital syphilis. Sera were reactive for 75%, 90.6%, and 33.8% using SPHA in the primary, secondary, and latent phases, respectively. The method gave 57.1% reactivity for the unclassified phase of syphilitic sera and 100% reactive for the congenital syphilitic sera. All 80 immunofluorescent nonreactive sera were nonreactive by SPHA. Of 19 reactive cord blood samples tested, seven samples were reactive by SPHA. However, all 20 nonreactive umbilical cord blood samples were nonreactive by SPHA. The SPHA assay for the determination of IgM antibody to T. pallidum in serum appears to be sensitive for primary, secondary, and congenital syphilis. The SPHA assay in the cord blood is sensitive and specific.