Diagnosis of congenital syphilis by combining Treponema pallidum-specific IgM detection with immunofluorescent antigen detection for T. pallidum.

Most infants at risk for congenital syphilis can be identified easily by a positive maternal serologic test for syphilis. However, a diagnosis of congenital syphilis can be difficult to make in an individual infant. Seven infants with delayed-onset congenital syphilis and 101 newborns at risk for congenital syphilis were evaluated for characteristic physical findings and laboratory-detectable abnormalities of congenital syphilis. By using a combination of Western blot for T. pallidum-specific IgM detection and immunofluorescent antigen detection for the identification of T. pallidum, a diagnosis of congenital syphilis was made in all 7 infants with delayed-onset congenital syphilis and 24 of the 101 newborns at risk for congenital syphilis. However, T. pallidum-specific IgM was negative in 6 of the 24 newborns with congenital syphilis. T. pallidum-specific IgM detection alone is inadequate for the diagnosis of congenital syphilis.