Identification of United States counties at elevated risk for congenital syphilis using predictive modeling and a risk scoring system

BACKGROUND: Although preventable through timely screening and treatment, congenital syphilis (CS) rates are increasing in the United States (US), occurring in 5% of counties in 2015. Although individual-level factors are important predictors of CS, given the geographic focus of CS, it is also imperative to understand what county-level factors are associated with CS. METHODS: This is a secondary analysis of reported county CS cases to the National Notifiable Disease Surveillance System (NNDSS) during 2014-15 and 2016-17. We developed a predictive model to identify county-level factors associated with CS and use these to predict counties at elevated risk for future CS. RESULTS: Our final model identified 973 (31.0% of all US counties) counties at elevated risk for CS (sensitivity: 88.1%; specificity: 74.0%). County factors that were predictive of CS included metropolitan area, income inequality, P&S syphilis rates among women and MSM, and population proportions of those who are non-Hispanic Black, Hispanic, living in urban areas, and uninsured. The predictive model using 2014-2015 CS outcome data was predictive of 2016-2017 CS cases (area under the curve value = 89.2%) CONCLUSIONS: Given the dire consequences of CS, increasing prevention efforts remains important. The ability to predict counties at most elevated risk for CS based on county factors may help target CS resources where they are needed most.