Evaluation of the BioPlex 2200 syphilis total screen (IgG/IgM) with reflex to an automated rapid plasma reagin test

Abstract

BackgroundWe evaluated the recently FDA cleared BioPlex 2200 Syphilis Total Screen and automated rapid plasma reagin (RPR) assay for the detection of total (IgG/IgM) treponemal and non‐treponemal antibodies in the reverse syphilis algorithm.MethodsProspectively submitted samples (n = 885) were assayed by both the IgG/IgM BioPlex Syphilis Screen and the original IgG BioPlex Syphilis Screen. The IgG screen reactive samples were reflexed to traditional RPR, and IgG/IgM screen reactive samples were reflexed to the automated RPR. Nonreactive RPR samples were tested by the Treponemal Pallidum Particle Agglutination test (TP‐PA). Additional samples were collected (n = 404 total samples) to directly compare the automated and traditional RPR assays with each other.ResultsThe sensitivity and specificity of the IgG/IgM screen with automated RPR was 95.6% (95% confidence interval [CI] 87.0‐99.1) and 99.6% (CI 99.2‐99.8) while the sensitivity and specificity of the BioPlex IgG screen with traditional RPR was 97.8% (CI 89.1‐99.9) and 99.3% (CI 98.8‐99.4). The sensitivity and specificity of the BioPlex RPR compared with traditional RPR was 95.8% (CI 93.9‐97.0) and 94.1% (CI 89.4‐91.1) and 95.3% (CI 92.6‐97.1). The mean of the titer differences between the BioPlex RPR and the traditional RPR was 1.0 ± 0.9 SD titers.ConclusionThe addition of the detection of treponemal IgM antibodies to the IgG/IgM screen did not significantly affect the sensitivity and specificity compared to the original IgG screen. However, the addition of the comparable BioPlex RPR assay to the instrumentation significantly reduces the overall labor of syphilis screening and confirmation.

Evaluation of the AIX1000 Automated Rapid Plasma Reagin Assay in a High-Prevalence Setting

“…[17][18][19][20][21] More recently, Bioplex 2200 integrated a treponemal and RPR assay on one analyzer with reported sensitivities for RPR ranging from 90.0% to 96.2%. 12,[22][23][24][25] A limitation of Bioplex 2200 RPR is the need for manual predilution of samples with titers <1:4 or >1:64. Next to AIX1000 and Bioplex 2200, also the ASI Evolution was approved by the Food and Drug Administration in 2020 for automated RPR analysis.…”

“…Other automated RPR assays such as Mediace, HiSens Auto RPR, and Sekure RPR have been developed previously, but sensitivities were lower when compared with manual RPR 17–21 . More recently, Bioplex 2200 integrated a treponemal and RPR assay on one analyzer with reported sensitivities for RPR ranging from 90.0% to 96.2% 12,22–25 . A limitation of Bioplex 2200 RPR is the need for manual predilution of samples with titers <1:4 or >1:64.…”

A 2021 Update on Syphilis: Taking Stock from Pathogenesis to Vaccines

“…Biological false positive, although uncommon, must be considered during pregnancy or autoimmune illnesses as well as other infectious diseases. Currently, NTT are manually performed and several attempts to automate these tests have been described [42]. Monitoring of nontreponemal test titer should be done using the same test and it is indicated to:…”

False-Positive Serologic Reactions for Syphilis

“…They concluded that the addition of the detection of treponemal IgM antibodies to the IgG/IgM screen had not significantly affected the sensitivity and specificity compared to the original IgG screen. But the addition of the comparable BioPlex RPR assay to the instrumentation significantly reduced the overall labor of syphilis screening and confirmation [72].…”