Evaluation of a Multiplex Fully Automated Treponemal and Nontreponemal (Rapid Plasma Reagin) Assay

OBJECTIVES: In June 2017, Bio-Rad Laboratories received US Food and Drug Administration clearance for its BioPlex 2200 Syphilis Total & RPR (rapid plasma reagin) assay. It is the first fully automated treponemal/nontreponemal multiplex flow immunoassay, simultaneously detecting Treponema pallidum and reagin antibodies and an RPR titer. We compared the performance of the BioPlex Syphilis Total & RPR assay with the LIAISON Treponema Assay and the manual BD Macro-Vue RPR 18-mm Circle Test. METHODS: In total, 314 serum specimens were tested for treponemal immunoglobulin G/immunoglobulin M and RPR with the LIAISON Treponema Assay, the BioPlex 2200 Syphilis Total & RPR assay, and the manual BD Macro-Vue RPR card test. All discordant results were further tested with the T pallidum particle agglutination assay from Fujirebio Diagnostics. RESULTS: The overall percent agreement for the BioPlex assay for treponemal antibodies with the LIAISON Treponema Assay was 96.1%. Sensitivity and specificity for the BioPlex RPR assay were 90.5% and 97.2%, respectively (the manual RPR assay was considered the gold standard). CONCLUSIONS: The BioPlex 2200 Syphilis Total & RPR assay performance was comparable to the LIAISON Treponema Assay and the manual RPR test. Compared with the manual RPR, the automation of RPR testing offered labor savings, objective result reporting, and improved workflow.