Comparison of Maternal and Newborn Serologic Tests for Syphilis

To compare the cord blood, newborn serum, and maternal serum for the diagnosis of congenital syphilis. —Retrospective chart review. —Kings County Hospital Center, Brooklyn, NY. —Three hundred forty-eight mother-newborn pairs with positive syphilis serology. —One hundred fifteen newborns (33%) had rapid plasma reagin tests of cord blood that were nonreactive. Their mothers had positive serologic findings. There were 10% false-positive cord blood samples (cord blood rapid plasma reagin tests reactive, newborn serum rapid plasma reagin tests nonreactive) and 5% false-negative cord blood samples (cord rapid plasma reagin tests nonreactive, newborn serum rapid plasma reagin tests reactive). Thirty-three newborns had congenital syphilis. Seven newborns had cord titers fourfold higher than their mothers'; only four of these newborns had congenital syphilis. Maternal serology is superior to cord blood analysis for identifying newborns at risk of congenital syphilis.