2F 4 Prenatal Syphilis Screening with the Reverse Sequence Algorithm: Analysis of Maternal and Neonatal Outcomes Among Women with Discordant Serology

Tuesday, June 10, 2014: 3:40 PM
Ina Park, MD, MS, Sexually Transmitted Disease (STD) Control Branch, California Department of Public Health, Richmond, CA, Okeoma Mmeje, MD, MPH, Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, Jeffrey Schapiro, MD, Kaiser Permanente Northern California (KPNC) Regional Laboratory, Berkeley, CA, Lisette Davidson, MD, MPH, Department of Obstetrics and Gynecology, Kaiser Permanente Northern California, Oakland, CA and Joan Chow, MPH, DrPH, Sexually Transmitted Disease Control Branch, California Department of Public Health, Richmond, CA

Background:  The reverse sequence algorithm (RSA) is increasingly used for prenatal syphilis screening by high volume laboratories, beginning with a treponemal test such as the chemiluminescene immunoassay (CIA), followed by reflex testing of CIA-reactive specimens with the rapid plasma regain test (RPR). Implications of discordant serology (CIA-reactive and RPR-non-reactive) for pregnancy and neonatal outcomes are unknown.  

Methods:  Pregnant women at Kaiser Permanente Northern California with CIA-reactive, RPR-non-reactive serology underwent reflex testing with Treponema pallidum particle agglutination (TPPA) from August 2007-August 2010.  Samples reactive with TPPA (CIA+, RPR-, TPPA+) were deemed “TPPA-confirmed”; those reactive only with CIA (CIA+, RPR-, TPPA-) were deemed “unconfirmed CIA-reactive”.  Past syphilis testing history, other medical history, maternal and neonatal outcomes and treatment were abstracted from the medical record.    

Results:  Of 194 pregnant women with discordant treponemal serology, 156 (80%) were unconfirmed CIA-reactive.  Of 106 women who were retested, 43 (41%) became CIA-non-reactive; all were initially unconfirmed CIA-reactive.  Women with TP-PA-confirmed serology were more likely to receive treatment for syphilis than those with unconfirmed CIA-reactive serology (31.5% vs 3.8% p<0.01).  Of 3 women who seroconverted to CIA-reactive and RPR-reactive during pregnancy, 1 became persistently CIA-non-reactive later in pregnancy and may have had both a false positive RPR and CIA.   A large majority of pregnancies (189, 97.5%) ended in a live birth; there were no stillbirths attributable to syphilis.  No infants were born with clinical signs of congenital syphilis, and 2 infants received antibiotic therapy based on the mother’s serology results.

Conclusions:  Most pregnant women with discordant treponemal serology were unconfirmed CIA-reactive and a substantial percentage became CIA-non-reactive upon repeat testing.   Isolated CIA-reactive serology in these populations is likely to be falsely positive.  Repeated testing of unconfirmed CIA-reactive specimens and reflex testing of discordant specimens with a second treponemal test is crucial in this population.