title: Discordant Syphilis Immunoassays in Pregnancy: Perinatal Outcomes and Implications for Clinical Management.
abstract: BACKGROUND
  The reverse sequence algorithm is often used for prenatal syphilis screening by high-volume laboratories, beginning with a treponemal test such as the chemiluminescence immunoassay (CIA), followed by testing of CIA-positive (CIA(+)) specimens with the rapid plasma reagin test (RPR). The clinical significance of discordant serology (CIA(+)/RPR(-)) for maternal and neonatal outcomes is unknown.
  
  
  METHODS
  From August 2007 to August 2010, all pregnant women at Kaiser Permanente Northern California with discordant treponemal serology underwent reflexive testing with Treponema pallidum particle agglutination assay (TP-PA) and were categorized as "TP-PA confirmed" (CIA(+)/RPR(-)/TP-PA(+)) or "isolated CIA positive" (CIA(+)/RPR(-)/TP-PA(-)). Demographic variables and clinical data were abstracted from the medical record and compared by TP-PA status.
  
  
  RESULTS
  Of 194 pregnant women, 156 (80%) were CIA(+)/RPR(-)/TP-PA(-) and 38 (20%) were CIA(+)/RPR(-)/TP-PA(+). Among the 77 (49%) CIA(+)/RPR(-)/TP-PA(-) women who were retested, 53% became CIA(-). CIA(+)/RPR(-)/TP-PA(+) (n = 38) women were more likely to be older, have a prior history of sexually transmitted infections, and receive treatment for syphilis during pregnancy than women who were CIA(+)/RPR(-)/TP-PA(-) (all P < .005). Most pregnancies (189/194 [97.5%]) resulted in a live birth; there was no difference in birth outcomes according to TP-PA status and no stillbirths attributable to syphilis.
  
  
  CONCLUSIONS
  Most pregnant women with discordant serology were CIA(+)/RPR(-)/TP-PA(-); more than half who were retested became CIA(-). CIA(+)/RPR(-)/TP-PA(-) serology in pregnancy is likely to be falsely positive. Reflexive testing of discordant specimens with TP-PA is important to stratify risk given the likelihood of false-positive results in this population.
authors.affiliation: Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor.
authors.forename: Okeoma
authors.initials: O
authors.lastname: Mmeje
authors.affiliation: Sexually Transmitted Disease Control Branch, Division of Communicable Disease Control, California Department of Public Health, Center for Infectious Diseases, Richmond.
authors.forename: Joan M
authors.initials: JM
authors.lastname: Chow
authors.affiliation: Department of Obstetrics and Gynecology, Oakland Medical Center.
authors.forename: Lisette
authors.initials: L
authors.lastname: Davidson
authors.affiliation: The Permanente Medical Group, Kaiser Permanente Northern California, Oakland.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Shieh
authors.affiliation: The Permanente Medical Group, Kaiser Permanente Northern California, Oakland.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Schapiro
authors.affiliation: Sexually Transmitted Disease Control Branch, Division of Communicable Disease Control, California Department of Public Health, Center for Infectious Diseases, Richmond Department of Family and Community Medicine, University of California, San Francisco.
authors.forename: Ina U
authors.initials: IU
authors.lastname: Park
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods* / Q000592:standards*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis* / Q000276:immunology / Q000628:therapy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D012189:Retrospective Studies; D013587:Syphilis / Q000175:diagnosis* / Q000276:immunology / Q000628:therapy; D013588:Syphilis Serodiagnosis / Q000379:methods* / Q000592:standards*
keywords: congenital syphilis; discordant treponemal serology; prenatal syphilis screening; prenatal syphilis treatment; treponemal immunoassay