Evaluation of a chemiluminescent microparticle immunoassay for determination of Treponema pallidum antibodies.

Evaluation of a Chemiluminescent Microparticle Immunoassay (CMIA) for determination of anti-Treponema pallidum (TP) antibodies, "ARCHITECT TPAb", was performed. This assay was confirmed to be a reliable anti-TP assay as it showed very good fundamental performance on reproducibility (intra-assay CV: less than 4%), assay specificity (100%, 500/500) and assay sensitivity (100%, 121/121). Since this assay showed very good dilution linearity for samples within the range of 0.59-8.38 S/CO, quantification of the immunoreactivity of anti-TP was attempted. The correction formula for quantification was successfully validated with 8 specimens. The quantified anti-TP, CMIA-QT, calculated by multiplying together the assay's corrected S/CO within the range of 0.59 - 8.38 and the sample dilution factors, showed a strong correlation with the titer of TP particle agglutination (TPPA). The clinical utility of CMIA-QT was evaluated with stored specimens from 5 primary, 5 secondary, and 5 neural syphilis patients. The clinical utility of CMIA-QT was confirmed in the same manner as that of TPPA.