Syphilis screening in pregnant women: Discordant results require careful confirmation

Abstract

In the past 15 years, many high volume clinical laboratories implemented reverse sequence syphilis screening. Reverse sequence screening uses an automated treponemal immunoassay as the initial screening step, instead of the traditional rapid plasma reagin. Reverse sequence screening is economical for high volume laboratories but has led to diagnostic difficulties when the testing algorithm yields discordant results, particularly for pregnant women. In this volume of The Journal, Williams et al evaluated 35 108 reverse sequence syphilis screening events among pregnant women in Ohio from 2011-2018. Overall, 127 women had discordant screening results, of which 85 (65%) were ultimately found to have a false positive treponemal immunoassay. These results suggest that for pregnant women in this cohort, discordant screening results were often secondary to false positive screening and were not indicative of syphilis infection. Interpretation of reverse sequence syphilis screening results is challenging in pregnant women, as the stakes are high for early diagnosis and treatment to prevent congenital syphilis. From 2013-2017, the CDC reported that the national rate of reported primary and secondary syphilis in women rose by 156%. In 2016, 628 cases of congenital syphilis were reported by CDC, with 41 cases of syphilis-related stillbirth. Congenital syphilis cases were concentrated in 9 regions across the US (Ohio was one of these areas), and the rise in syphilis in women has been linked to the amphetamine and opioid epidemics. Thus, the results reported by Williams et al require careful interpretation in the context of local epidemiology. Nevertheless, this study highlights the challenges of interpreting screening assays that may offer convenience over specificity and underscores the need to perform confirmatory testing for pregnant women with discordant syphilis screening results. Article page 263 ▸