Prevalence and Epidemiological Profile of VDRL Seroreactivity Among Blood Donors in the Brazilian Amazon

(1) Background: To analyze the prevalence, temporal trends, and epidemiological pro-file of VDRL seroreactivity among blood donors deemed ineligible due to syphilis in the 1st Social Protection Region of the State of Pará, Brazil, between 2017 and 2023. (2) Study design and methods: This was a cross-sectional, retrospective, census-based epidemiological study conducted using secondary data from the SBS.Web system of the Pará State Hemotherapy and Hematology Center Foundation. All donations with reactive VDRL results in laboratory screening were included. Descriptive and inferential analyses were performed, including temporal trend analysis, prevalence estimates, correlation between municipal rates, and hierarchical clustering analysis, adopting a significance level of 5%. (3) Results: Among 362,705 recorded donations, 3730 (1.02%) showed VDRL seroreactivity. The mean age was 37.6 ± 11.5 years, with a progressive decrease over the study period and a higher concentration among young adults. There was a predominance of males (51%), single individuals (71.5%), those with secondary education (61.7%), and self-reported mixed-race individuals (82.2%). Belém accounted for 67.9% of cases and was the only municipality with a significant increasing trend. The highest mean prevalence rates were observed in Marituba and Barcarena. A strong positive correlation was identified between prevalence rates in Belém, Ananindeua, and Marituba, indicating high epidemiological similarity among these municipalities. (4) Conclusion: VDRL seroreactivity showed a heterogeneous sociodemographic, temporal, and territorial distribution, with greater concentration in urbanized and socially vulnerable areas. These findings reinforce its usefulness as an indirect indicator of population exposure and as a tool to support planning within the blood network and regional epidemiological surveillance.