[Diagnosis of congenital syphilis at delivery: maternal serum or cord blood?].

UNLABELLED Congenital syphilis (CS) is an important health problem in Chile, with a rate of 0.25/1,000 live newborn (NB) during year 2004. In 2000, the Chilean Ministry of Public Health recommended to perform a screening in cord blood at the moment of delivery. Instead, the Centers for Disease Control and Prevention guidelines recommend the screening in maternal serum since cord blood has up to 5% of false (-) versus 0.5% of maternal serum, both with respect to the NB serum. OBJECTIVE Maternal serum and NB cord blood were studied during one year to determine the best screening method at delivery. METHODS RPR was performed and positive results were confirmed by treponemic test (immunochromatographyDetermine, ELISA Captia, Ig and IgM, and MHA-Tp). Serologically confirmed patients were evaluated by the specialist to define CS cases. RESULTS Between June 1999 and August 2000 2,741 binomies were studied; of these, 37 (1.3%) were RPR reactive and 2.704 were non-reactive. In 11 of the 37 reactive cases, mother and NB were RPR reactive (Group I), in 9 cases the NB was RPR reactive and the mother was non-reactive (Group II), and the other 17 were NB non-reactive and mother reactive (Group III). In group I, 7/11 (64%) were true (+)s and 4/11(36%)) false (+)s of RPR. In group II, 9/9 (100%) corresponded to false (+)s of RPR in cord blood, and in group III, 11/17 (65%) corresponded to false (+)s of RPR in maternal blood but 6/17 (35%) were found to be cases of syphilis during pregnancy. Three of them were not treated opportunely and were designed as CS. In total 9 NB corresponded to CS (6 in group I and 3 in group III). If the screening had been performed only in cord blood, three NB with CS would have not been diagnosed. CONCLUSION Even when maternal serum has a high rate of false (+)s, it has better sensitivity than cord blood for the diagnosis of CS, thus it is suggested to perform the screening at delivery with maternal serum instead of cord blood samples.