[Syphilis and pregnancy. Prenatal control, seroprevalence and false biological positives]

Syphilis may be transmitted vertically, especially if the mother is in an early stage with a high bloodstream treponema concentration, although it may also be transmitted to a lesser degree in late latency, when non-treponemic serology may become negative spontaneously with persistence of treponemic serology. The prenatal control for syphilis is routinely carried out by means of a non-treponemic reaction such as VDRL or rapid plasma reagin (RPR) which, when positive, should be confirmed by treponemic techniques such as fluorescent treponemal antibody absorption (FTA-abs) and/or hemagglutination (MHA-Tp). Prevalence of syphilis should be defined on the basis of positive treponemic reactions. To define the seroprevalence and the validity of these control guidelines, 1,056 pregnant women attending the Hospital de Clínicas for their initial control were evaluated by means of serological treponemic and non-treponemic methods. Serological results disclosed 4 distinct groups. Group 1 (n = 17 or 1.61%) presented both types of reactive tests, while Group II (n = 22 or 2.08%) only presented reactive treponemic tests, and both groups were seroreactive for syphilis. Group III (n = 7 or 0.66%) only showed reactive non-treponemic tests, which were considered biological false-positive (BFP) reactions. Five of them were reactive for antiphospholipid antibodies. Group IV (n = 1,010 or 95.65%) fell to present serological evidence of syphilis. To conclude: 1) global seroprevalence in this population was 3.69%; 2) since 2.08% of pregnant seroreactive mothers had not been detected by routine screening, it would be advisable to perform simultaneous treponemic and non-treponemic techniques for prenatal control. 3) This methodology should identify the BFP tests in the same screening.