Analysis of syphilis antibody results in pregnant women and newborns detected by automatic chemiluminescent immunoassay / 中华检验医学杂志

ABSTRACT

Objective:To examine the distribution of syphilis antibody in pregnant women and newborns and to explore how to optimize the existing syphilis screening process by setting the diagnostic gray area.Methods:The results of syphilis testing obtained from 119 531 pregnant women and 21 275 newborns from 2015 to 2018 by automatic chemiluminescent immunoassay (CLIA) and the re-examination results determined by Treponema pallidum particle agglutination (TPPA) and the rapid plasma reagin test (RPR) were retrospective analyzed. Data analysis was performed by Chi-square, Fisher′s exact test and Chi-square test for trend. Results:The positive rates of Syphilis specific antibody (TPAb) in clinical specimens from pregnant women and newborns were 0.69% (825/119 531) and 1.24%(264/21 275). The total re-examination positive rates were 0.32% (380/119 531) and 0.90%(191/21 275), and the suspicious syphilis prevalence rates in these specimens were 0.13% (161/119 531) and 0.31%(67/21 275), respectively. The suspicious syphilis prevalence rates in specimens of pregnant women from 2015 to 2018 and newborns increased year by year (χ 2=9.860, P=0.002; χ 2=5.311, P=0.021). With the elevation of the optical density value of samples to cut-off ratio (S/CO) value, positive coincidence rate of TPPA and TPAb in pregnant women and newborns increased significantly (χ 2=614.833, P<0.001; P<0.001). When the S/CO value in newborns exceeded 7.00 or the S/CO value in pregnant women exceeded 15.00, the effectiveness of TPAb results is equivalent to TPPA. The prevalence of suspected syphilis in pregnant women and newborns also increased with the increase of S/CO value (χ 2=323.059, P<0.001; P<0.001). When the S/CO value in newborns bellowed 3.00 or the S/CO value in pregnant women bellowed 5.00, the prevalence rate of suspected syphilis was 0%, which could preliminarily exclude syphilis infection. Conclusions:The prevalence rates of suspected syphilis in pregnant women was increasing during the recent years. It is necessary to further strengthen syphilis screening and intervention treatment in early pregnancy to improve the rate of eugenics. Being a primary screening method for syphilis in pregnant women and newborns, CLIA has high false positive rate. According to the gray area established in this study, the syphilis screening process can be optimized to prevent missed detection, which may reduce the false positive rate and avoid clinical misdiagnosis.