Syphilis is a public health problem with traditional surveillance limited to clinical monitoring data; asymptomatic and low-risk populations rarely undergo diagnostic testing. Globally, the syphilis prevalence has consistently increased over the last years, worldwide. Blood donation screening can provide valuable information on syphilis trends over time and on the occurrence of undetected cases in the community.

To evaluate the rates and the relationship between syphilis positivity in blood donors when compared against the notifications of sexually acquired syphilis, syphilis in pregnant persons, and congenital syphilis reported by the Brazilian surveillance system between 2012 and 2022.

Data was compared directly to evaluate the correlations between deferral rates due to syphilis in first-time donors within the REDS-IV-P blood centers (per 100,000 donations); annual rates of syphilis reactivity among Brazilian blood donors obtained from the Hemotherapy Bulletin (HEMOPROD; per 100,000 donations); and rates of congenital syphilis (per 1,000 live births), sexually acquired syphilis (per 100,000 population), and syphilis in pregnant persons (per 1,000 live births) in Brazil extracted from official reports published by the Ministry of Health. The deferral rates in blood donations were based on the results of screening tests.

We observed an increase in syphilis detection over time by all definitions between 2012 and 2022, with a more pronounced increase in syphilis in pregnant persons (5.7x) and sexually acquired syphilis (7.0x), except for 2020, likely due to underreporting secondary to the COVID-19 pandemic. The increase in deferral rates for syphilis in blood donors in Brazil and in REDS was less sharp (1.6x and 1.4x respectively) when compared to the rates for sexually acquired syphilis and gestational syphilis. REDS-IV-P data reflected the country's deferral pattern, approximately correlating with the increase in congenital syphilis detection rates (2.5x) in the period.

There is a close correlation between syphilis rates in first-time blood donors and congenital syphilis rates recorded by the surveillance system between 2012 and 2022. Donors have lower syphilis rates than the overall adult population and a less pronounced increase in rates over time, probably due to sociodemographic and behavioral characteristics of the blood donor population.