Screening and diagnosis of syphilis in pregnant women without prior syphilis

STI: sexually transmitted infection.
* The initial type of screening test (treponemal versus nontreponemal) is typically dictated by the clinical laboratory.
¶ Nontreponemal tests include the rapid plasma reagin (RPR), the Venereal Disease Research Laboratory (VDRL), and the toluidine red unheated serum test (TRUST).
Δ Treponemal tests include the fluorescent treponemal antibody absorption (FTA-ABS), the Treponema pallidum particle agglutination (TPPA), the T. pallidum enzyme immunoassay (TP-EIA), or chemiluminescence immunoassay (CIA). These different treponemal tests target different antigens.
◊ Refer to the topic that discusses syphilis and pregnancy for treatment regimens.
§ A reactive low titer nontreponemal screening test can be considered a transient biologic false-positive result due to pregnancy if the confirmatory treponemal test is negative and the patient is asymptomatic and at low risk of acute syphilis. False-positive nontreponemal test results can also be related to an acute event, such as an acute febrile illness or recent immunization. Test abnormalities attributed to these conditions are usually transitory and typically last for 6 months or less.
¥ If at 28 to 32 weeks gestation a screening nontreponemal test (eg, RPR) is reactive and the confirmatory treponemal test (eg, FTA-ABS) is nonreactive, treatment is usually the best option rather than repeating a confirmatory treponemal test in 2 to 4 weeks. If at 28 to 32 weeks a screening treponemal test is reactive and the confirmatory nontreponemal test is nonreactive, a second treponemal test that targets different antigens should be performed; if positive, serology is consistent with syphilis, and, if negative, syphilis is unlikely. However, if there is diagnostic uncertainty (eg, a second treponemal test cannot be performed) in the setting of pregnancy, we prefer to treat.
‡ Testing performed at delivery is used to help inform the pediatrician regarding screening/treatment of the newborn. Treatment of the mother at delivery does not prevent transmission.