Comparison of maternal and newborn serologic tests for syphilis

Abstract

Objective: To compare the cord blood, newborn serum, and maternal serum for the diagnosis of congenital syphilis.

Design: Retrospective chart review.

Setting: Kings County Hospital Center, Brooklyn, NY.

Patients: Three hundred forty-eight mother-newborn pairs with positive syphilis serology.

Measurements and results: 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.