Contact tracing of syphilis-seropositive pregnant women and syphilis-infection among their male partners in Bao'an district, Shenzhen, China

The Shenzhen Program for Prevention of Congenital Syphilis (SPPCS) is a citywide program supported by the Bureau of Health (now the Health Commission) of Shenzhen Municipality. Initiated in 2001, SPPCS covers all antenatal clinics (ANCs) in Shenzhen city and offers free syphilis screening for all pregnant women at their first antenatal clinic visits. According to the SPPCS guidelines, syphilis-seropositive was defined as positive results in both toluidine red unheated serum test (TRUST, Shanghai Rongsheng Bio Tech Co, Ltd., Shanghai, China) and treponemal pallidum particle agglutination (TPPA, Fujirebio Inc., Tokyo, Japan [8]. All syphilis-seropositive pregnant women were encouraged to notify their male partners for further examinations. Three partner notifying approaches were recommended: patient referral, in which the pregnant women notify partners by themselves; provider referral, where doctors notify partners with pregnant women’s permission; contract referral, in which pregnant women agree to notify partners, but doctors may intervene if the partners do not present for treatment. Male partners presented to the clinics were recommended for syphilis-screening with both TRUST and TPPA, and if positive, were referred for further treatment [9]. Information of syphilis-seropositive pregnant women and male partner attending clinics for syphilis-screening were collected by the doctor using a self-developed structured questionnaire (presented in Additional files). The current study samples were drawn from SPPCS datasets and included pregnant women who were syphilis-seropositive and their male partners attending clinics for syphilis-screening in Bao’an District from 2012 to 2017. Considering the relatively stable sex relationships of pregnant women, their male partners traced in this study were limited to the closest one for each pregnant woman, mainly referring to spouse of the married and the closest male partner during the past 12 months for the unmarried or divorced. Syphilis-seropositive pregnant women and their male partners with complete information were finally included for analyses.

According to the SPPCS guidelines [8], syphilis-seropositive pregnant women were interviewed in a separate consulting room by the doctor and received a physical examination. Based on the results of the interview and physical examination, the doctor completed the self-developed structured questionnaire (presented in Additional files). Information of their male partners presenting to clinics for further examination was also collected by the doctor. Data of pregnant women and their male partners analyzed in the current study included: demographic characteristics (i.e., age, ethnicity, education, marital status, occupation, and residency status), history of past illness (i.e., history of drug abuse, history of syphilis or other STDs), obstetrical history (i.e., age at first sex, number of lifetime sexual partners, history of APOs), and history of present illness (i.e., pregnancy status at the first ANC visits, syphilis test results, staging diagnosis of syphilis, willingness to notify partner and partner notifying approaches).

The primary outcomes of interest included contact tracing rate estimated as the proportion of syphilis-seropositive pregnant women whose partners received syphilis-screening, syphilis prevalence among male partners estimated as the proportion of male partners infected with syphilis, and their 95% confidence interval (CI). Characteristics of pregnant women listed in Table 1, as well as women’s staging diagnosis of syphilis, TRUST titer, willingness to notify partner and partner notifying approaches were tested as possible variables related to contact tracing. Characteristics of male partner listed in Table 1, as well as women’s staging diagnosis of syphilis, TRUST titer, number of lifetime partners and source of syphilis infection on pregnant women’s reports were tested as possible variables related to syphilis-infection among male partners. We explored potential variables related to contact tracing and syphilis-infection among male partners by using multivariate logistic regression models to estimate adjusted odds ratio (AOR) and 95% CIs. For all analyses, P values < 0.05 were regarded as statistically significant. All analyses were performed using SPSS for Windows software (version 17.0).

Between January 1st, 2012 and December 31st^, 2017, 626,446 pregnant women were screened for syphilis and 1302 were identified to be syphilis-seropositive as having positive results in both TRUST and TPPA. A total of 1299 syphilis-seropositive pregnant women with complete available information were enrolled. 963 male partners of syphilis-seropositive pregnant women presented to clinic and received screening for syphilis. Data of 1299 syphilis-seropositive pregnant women and 963 male partners were included for analyses.

Characteristics of 1299 syphilis-seropositive pregnant women are presented in Table 1. The pregnant women had a mean age of 28.81 (SD = 5.85, range: 16–49). Most pregnant women presented to the clinics for routine antenatal care at their first ANC visits (n = 936, 72.1%), and the rest presented for emergency services, including in labor (n = 165, 12.7%), spontaneous abortion (n = 43, 3.3%), stillbirth (n = 25, 1.9%), ectopic pregnancies (n = 120, 9.2%), and artificial abortions or inductions of labor (n = 10, 0.8%). 10 (0.8%) women having existing symptoms of early syphilis in the physical examination at their first ANC visits, 419(32.3%) women having a history of syphilis and having been treated before pregnancy, and 870 (67.0%) women lacking existing symptoms of syphilis in the physical examination and without anti-syphilis treatment before pregnancy were diagnosed as early syphilis, syphilis after adequate treatment, and latent syphilis, respectively. TRUST titer ranged from 1:1–1:256, with the majority under 1:8 (n = 954, 73.4%). 418(32.2%) of pregnant women had first sex at the age of 20 and younger, and 652(50.2%) reported more than one lifetime sex partners.

Characteristics of 963 male partners are presented in Table 1. The male partners had a mean age of 31.50 (SD = 6.53, range: 17–56).429(44.5%) of male partners had first sex at the age of 20 or younger, and 377(39.1%) reported more than one lifetime sex partners.

Among the 1299 syphilis-seropositive pregnant women, 1205(92.8%) stated willingness to notify their male partners, and 94 (7.2%) reported that they did not want to notify their male partners. The barriers to partner notify reported by the pregnant women included fear of relationship breakdown (n = 82, 87.2%), lack of contact information because of having divorced or separated with partners (n = 10, 10.6%), fear of social discrimination (n = 1, 1.1%), and distrust of the diagnosis (n = 1, 1.1%). 1191 (91.7%) of the syphilis-seropositive pregnant women selected patient referral, 66 (5.1%) selected provider referral and 42 (3.2%) selected contract referral. Finally, 1155(88.9%) pregnant women reported that their partners were notified, 985 (75.8%) partners presented to the clinics and 963 (74.1%) male partners received screening for syphilis, resulting in a contract tracing rate of 74.1% (95% CI, 72.9–75.3%).

Factors independently associated with contact tracing in a multivariate regression model are showed in Table 2. Pregnant women being divorced (adjusted odds ratio [AOR] =0.39; 95%CI: 0.17–0.87), seeking for emergency services at their first ANC visits (AOR =0.58; 95%CI: 0.44–0.77), reporting willingness to notify partner (AOR = 7.65; 95%CI: 4.69–12.49), multi-partners (AOR = 1.38; 95%CI: 1.03–1.86) and having a history of drug abuse (AOR = 0.37; 95%CI: 0.14–1.00) were independently and significantly associated with successful contact tracing.

Among the 963 male partners screened for syphilis, 779 (80.9%) were negative in both TRUST and TPPA, 155 (16.1%) were positive in both TRUST and TPPA, 29 (3.0%) were positive only in TPPA, leading to a syphilis prevalence of 19.1% (184/963).

Factors independently associated with syphilis infection among male partners in a multivariate regression model are shown in Table 3. For pregnant women, TRUST titer ≥1:8 (AOR = 2.81; 95%CI: 1.87–4.21), syphilis infection from the current partner (AOR = 5.05; 95%CI: 2.82–9.03), multi-partners (AOR = 0.43; 95%CI: 0.29–0.64), history of APOs (AOR = 1.70; 95%CI: 1.14–2.53) were all independently and significantly associated with syphilis-infection of their male partners. For the male partners themselves, of minority ethnicity (AOR = 4.15; 95%CI: 1.66–10.34), age at first sex > 20 years old (AOR = 0.57; 95%CI: 0.37–0.87), multi-partners (AOR = 1.60; 95%CI: 1.04–2.46), and history of drug abuse (AOR =4.07; 95%CI: 1.31–12.64) were all independently and significantly associated with their own syphilis-infection.