Background Serologic tests for syphilis remain the mainstay of diagnosis. However, diagnosis of congenital syphilis is complicated by the passive transfer of maternal antibodies to the infant. Non treponemal test (NTT) titres should decline by age 3 months and should be non reactive by age 6 months if the infant was not infected or was infected but adequately treated. Limited data exist on the serologic outcome of treponemal tests (TT) in cases with clinical or laboratory evidence of congenital syphilis at birth.
Methods Cases meeting Canadian surveillance criteria for confirmed early congenital syphilis [within 2 years of birth] (http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/09vol35/35s2/Syphilis-eng.php) were reviewed from the Alberta Health Services Edmonton zone from 2005 to 2010. Under Alberta's Public Health Act, maternal stage, treatment information and serologic follow-up and infant clinical, laboratory and treatment information are obtained and stored in a provincial STI database.
Results 22 cases met surveillance criteria for confirmed congenital syphilis: six were either stillborn/deceased at birth, three are still under 18 month serologic follow-up, one had persistently reactive TT (21 months) and four had reactive TT at the end of their follow-up period (ages 11, 12, 13 and 15 months). 3/5 cases with persistently reactive TT were treated with 9–10 days of intravenous penicillin within 0–2 days of birth, 1 at 3 months of age and 1 at 8 months of age. In 4/5 of these cases, the RPR had reverted to non reactive at the end of the follow-up period while in the 5th case (treated at 8 months), the RPR declined from a titre of 1:4096 dilutions at birth to 1:64 dilutions at 11 months of age. The remaining eight cases had negative TTs, as summarised in the table. All were treated with 10 days of intravenous penicillin (except case #2 treated with 9 days) see Abstract P3-S6.03 table 1.
Conclusions As with early treatment of primary syphilis cases, seroreversion of TT can occur in cases meeting clinical and laboratory criteria for congenital syphilis. Seroreversion was observed with older TT such as TPPA and FTA-ABS as well as the newer syphilis EIA.
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