Recombinant antigen-based enzyme immunoassay for screening of Treponema pallidum antibodies in blood bank routine.

This work reports a comparison of an enzyme immunoassay (EIA) using two major Treponema pallidum recombinant antigens with a T. pallidum hemagglutination (TPHA) assay and a nontreponemal Venereal Disease Reference Laboratory (VDRL) test. A total of 1,822 normal donor serum samples was tested for cardiolipin and T. pallidum antibodies, respectively, by the VDRL assay and EIA. Among these samples, 440 were further tested by TPHA technology. Four samples were found positive by EIA, while all were reported to be negative by both TPHA and VDRL routine assays. Subsequent testing of EIA-positive samples confirmed 100% (four of four samples) and 25% (one of four samples) positive results, respectively, by immunofluorescence assay and a Western blot (immunoblot) syphilis kit. The sensitivity of the recombinant EIA was estimated at virtually 100% with a reference panel of 50 syphilitic samples. According to this study, the newly developed EIA kit shows 100% sensitivity combined to a specificity greater than 99.8% for detecting treponemal immunoglobulin G antibodies in blood bank syphilis screening.