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Poster Session I: Congenital Syphilis & Syphilis in Pregnancy

(P24) POTENTIAL IMPACT OF MODIFYING THE CONGENITAL SYPHILIS CASE DEFINITION ON CASE COUNTS IN NEW YORK CITY, 2011-2022

Tuesday, September 17, 2024
4:15 PM - 5:15 PM EST
Background:
Clinical guidance recommends treatment for syphilis-exposed infants who have a reactive nontreponemal titer fourfold or greater than the maternal titer at delivery; however, the probable congenital syphilis (CS) surveillance case definition requires additional laboratory/clinical findings, leading to confusion between providers and surveillance staff. We determined the additional case burden in New York City (NYC) if a modified CS case definition were used that included infants with a fourfold or greater titer difference without additional criteria.

Methods:
We analyzed NYC syphilis registry data from 2011-2022. We identified syphilis-exposed births that 1) did not meet the surveillance case definition for probable CS and 2) the infant had a reactive nontreponemal titer that had a linked maternal event with a reactive nontreponemal titer within 14 days of delivery.  Using tests that were collected at/or closest to delivery, we identified how many additional births would have been considered cases based on titer difference alone.

Results:
Between 2011-2022, 160 births met the probable CS case definition, and 871 births did not. Of those that did not, 6 (0.7%) infants had a titer fourfold or greater than the maternal titer at delivery without additional laboratory/clinical findings. Most (4/6, 67%) infants had titers exactly fourfold higher than the maternal titers; infant titers were 1:4, 1:8, and 1:16, with maternal titers of 1:1, 1:2, and 1:4, respectively. One infant had an eightfold titer difference (infant titer: 1:16; maternal titer: 1:2), and one had a 16-fold difference (infant: 1:16; maternal: 1:1).

Conclusion:
Most infants with a reactive nontreponemal test have titers equivalent to or less than the maternal titer at delivery. Modifying the CS case definition to include infants with a nontreponemal titer at delivery of fourfold or greater than the maternal titer without any additional clinical/laboratory criteria would not substantially increase the burden of CS cases in NYC.