The Accuracy of Group Beta Streptococcus Rectovaginal Cultures at 35 to 37 Weeks of Gestation in Predicting Colonization Intrapartum

Abstract

Objective This study aims to investigate accuracy of group beta Streptococcus (GBS) rectovaginal cultures at 35 to 37 weeks in predicting intrapartum colonization. Study Design Institutional review board (IRB) approved prospective cohort study of 302 women from October 2015 to May 2017. Patients had the following tests for GBS: first trimester urine culture, rectovaginal culture at 35 to 37 weeks, and intrapartum rectovaginal culture. Outcomes included accuracy of 35- to 37-week GBS rectovaginal culture in detecting results intrapartum, and accuracy of first trimester urine culture in comparison to intrapartum rectovaginal cultures. Results There was sufficient evidence of agreement between results at 35 to 37 weeks with intrapartum cultures (p = 0.001). However, agreement was weak, 11 patients (3.7%) were GBS positive intrapartum but negative at 35 to 37 weeks; and 33 patients (11%) were initially GBS positive but were negative intrapartum. Sensitivity and specificity of the 35- to 37-week culture was 69% (95% confidence interval [CI]:54–84%) and 87% (95% CI: 83–91%), respectively. There was also weak agreement between first trimester urine culture and intrapartum rectovaginal culture. Specificity for this assessment was 98% (95% CI: 97–100%) and was significantly different compared with antepartum GBS culture (p < 0.001). Accuracy between antepartum GBS rectovaginal culture and urine culture was similar (85 vs. 87%, p = 0.47). Conclusion The 35- to 37-week GBS rectovaginal culture might be a poor predictor for intrapartum colonization.

Group B Streptococcus and the vaginal microbiome among pregnant women: a systematic review

“…In a study by McCoy and colleagues, nearly 40% of women that were positive at GBS screening were not GBS positive at the time of admission ( McCoy et al., 2020 ). Alternatively, Hussain et al. (2019) reported a discordance rate of 11%.…”

“…This suggests that there may be a benefit to using both sequence-based and culturebased methods to verify presence or absence of low abundance microbes within vaginal microbiome communities. Previous studies have shown discordance in culture-based GBS colonization results between antenatal screening and culture on admission for delivery (McCoy et al, 2020;Hussain et al, 2019). In a study by McCoy and colleagues, nearly 40% of women that were positive at GBS screening were not GBS positive at the time of admission (McCoy et al, 2020).…”

“…In a study by McCoy and colleagues, nearly 40% of women that were positive at GBS screening were not GBS positive at the time of admission (McCoy et al, 2020). Alternatively, Hussain et al (2019) reported a discordance rate of 11%. While the transient nature of GBS colonization is known, factors that contribute to loss or gain of maternal GBS colonization remain uncertain (Hansen et al, 2004).…”

Peer Review #1 of "Group B Streptococcus and the vaginal microbiome among pregnant women: a systematic review (v0.1)"

“…This suggests that there may be a benefit to using both sequence-based and culture-based methods to verify presence or absence of low abundance microbes within vaginal microbiome communities. Previous studies have shown discordance in culture-based GBS colonization results between antenatal screening and culture on admission for delivery 6,58 . In a study by McCoy and colleagues, nearly 40% of women that were positive at GBS screening were not GBS positive at the time of admission 6 Manuscript to be reviewed of 11% .…”

Performance of the HiberGene Group B Streptococcus kit, a loop-mediated isothermal amplification–based assay for GBS screening during pregnancy

“…Indeed, it has been shown that GBS carriage fluctuates during the pregnancy and more particularly from 35 to 37 weeks and the onset of labor. Reversion of 35-37 weeks GBS carriage occurs in about 10% of the cases and about 4% of negative GBS carriers are detected as positive at the onset of labor [3]. The use of molecular assays for GBS peripartum screening allows for targeting the correct population with analytical performances equivalent to culture [4].…”