False negative screening tests for syphilis in pregnant women

To the Editor: A recent increase in the prevalence of syphilis and congenital syphilis has been noted in the United States, reaching epidemic proportions in some areas.¹ Controlling this epidemic depends on the identification and treatment of infected women. The true disease state may be misidentified in some clinical situations. False negative results on routine nontreponemal testing may occur in pregnancy during the active disease as a result of the prozone phenomenon. This phenomenon occurs when there is an excess of antibody in the serum samples being examined such that the formation of the antibody—antigen lattice network required for flocculation.