Evaluation of False Positive RPR Results and the Impact of SARS-CoV-2 Vaccination in a Clinical Population with a High Rate of Syphilis Utilizing the Traditional Screening Algorithm

Abstract Background Syphilis infection caused by the bacterium Treponema pallidum is a sexually transmitted leading to serious health complications if undiagnosed or untreated. Serologic diagnostic methods include combined approach for detection of antibodies non-treponemal (RPR) and treponemal antigens using traditional reverse algorithm. The BioPlex2200 Total/RPR assay (BioRad Laboratories) an automated method simultaneous treponemal/non-treponemal antibodies, but recently recalled due potential RPR false reactivity following SARS-CoV-2 mRNA vaccination. purpose this study was evaluate syphilis confirmation positive rates over various intervals preceding during COVID-19 pandemic in population with high rate syphilis, subset pregnant females screened prior delivery, assess impact vaccines on different methodologies. Methods cohort included all individuals (n=48,288) patients (n=2,944), where testing ordered routine clinical care utilizing Five timepoints represented phases utilized throughout pandemic: 1) pre-COVID-19 (automated RPR, July – December, 2019); 2) COVID-19, pre-mRNA vaccine (manual 2020); 3) January June, 2021); 4) vaccine/boosters August 5) (RPR/T.pallidium sent out reference laboratory, February, 2022). False defined as reactive RPR/nonreactive T.pallidium. Titers were determined specimens. Results between 4.5 7.9% 0.15 0.41% entire period. increased screening (5% 8.6%) groups (4.4% 7.5%) from 2019 2021. Comparing only timepoint 1 (2019) 4 (end 2021), both reporting overall 8.2% 14.1% 4.8% 7.8% cohort. No significant differences observed manual (5.2% vs. 6.3%) (1.3% 1.2%) pre- post-vaccination (reactivity rates: 0.68% 0.29%; positives: 0.27% 0.15%). Over 90% positives had titers less than 1:4. RPRs decreased 8.6% 2.9% implementation sendouts. Conclusions vaccination specific which has improved analytical sensitivity anti-lipoidal compared methods, thus may be more susceptible post-vaccination. Increased clinically notable likely because algorithm at our institution.