B-190 Increasing Syphilis Positivity and the Importance of Validated Rapid Testing for Early Diagnosis and Disease Control Strategies

Abstract

Syphilis is a bacterial sexually transmitted infection (STI) caused by the bacterium Treponema pallidum. The diagnosis of infection requires the performance of treponemal and non-treponemal laboratory tests. Brazil has shown a marked increase in the number of syphilis cases over the years, representing a significant public health concern, as reported in the Brazilian Syphilis Epidemiological Bulletin. In this context, Point-of-Care Testing (POCT) has assumed a relevant role in confirming diagnosis due to its broad availability in Primary Health Care Units and the rapid turnaround time of results, typically ranging from 5 to 20 minutes. This study aimed to evaluate syphilis positivity using clinical laboratory data and to assess the performance of a treponemal POCT. Positive syphilis cases were retrospectively evaluated using data from the Shift Laboratory Information System (LIS), including Venereal Disease Research Laboratory (VDRL) tests collected between 2018 and 2025. The study population included male and female individuals, including pregnant women. Annual trends in positivity were assessed by calculating the year-to-year percentage increase in VDRL-reactive results. For POCT validation, a qualitative comparative analysis was performed using 28 serum samples processed on the Cobas E-801 system (electrochemiluminescence immunoassay –treponemal) using the Elecsys Syphilis reagent (Roche ®), VDRL (non-treponemal) with the VDRL test reagent (Wiener lab®), and the GT® Syphilis rapid test (POCT- treponemal). The performance of POCT was evaluated using agreement analysis and the kappa coefficient. Data analysis was conducted using EP Evaluator software, version 12.4, (Data Innovations). A total of 1,556,464 VDRL requests were recorded, of which 12.1% (188,288) were positive, with 66.8% occurring in females, of whom 13.4% were pregnant women, between 2019 and 2025. The annual positivity rate was: 5.9% (2018), 9.4% (2019), 10.9% (2020), 9.6% (2021), 13.2% (2022), 13.4% (2023), 13.5% (2024), and 14.1% (2025). An overall increase in syphilis positivity of 139.6% was observed between 2018 and 2025. The most significant rise was noted between 2018 and 2019 (59.8%), followed by an increase between 2021 and 2022 (36.7%). The performance evaluation of the rapid test was conducted through agreement analysis and the kappa coefficient. In the comparison between the Cobas method and the POCT, both agreement and kappa were 100%, indicating perfect concordance. In the comparison between VDRL and the POCT, agreement was 96.4% with a kappa of 92.9%. When analyzing the relationship among the three methods (Cobas, VDRL, and POCT), overall agreement was 98.2%, with a kappa coefficient of 96.4%. A significant increase in syphilis positivity was observed throughout the study period, underscoring its continued relevance as a major public health concern. Notably, positivity rates remained stable during the COVID-19 period but increased markedly in the post-pandemic period. The GT rapid test demonstrated excellent agreement with both treponemal (Cobas) and non-treponemal (VDRL) reference methods, proving to be a reliable and effective tool for supporting syphilis diagnosis and screening, particularly in settings that require rapid results and broad access within the Brazilian Unified Health System (SUS). The use of POCT may support disease control strategies and contribute to preventing congenital syphilis.