Abstract / Summary
Abstract Purpose Vertical transmission of Group B Streptococcus (GBS) during childbirth can cause severe neonatal infections. Vaginal-rectal screening enables intrapartum antibiotic prophylaxis for women with maternal GBS colonisation. Although real-time PCR is highly sensitive, culture remains the recommended method for antenatal GBS screening. Due to dynamic recto-vaginal GBS colonisation in pregnant women, determining optimal timing for antenatal screening remains challenging. This Belgian multicentre study aimed to assess the predictive window of antepartum screening with real-time PCR to reliably predict maternal GBS colonisation at delivery. Methods This study first evaluated the Panther Fusion® GBS real-time PCR assay (Hologic®) for antenatal GBS screening at 35–37 weeks of gestation (n = 1353). Specimens were analysed using non-enriched PCR, broth-enriched PCR, and broth-enriched culture. To assess the predictive window of antenatal GBS screening, a subset of women also provided intrapartum samples for PCR and culture analysis (n = 257). Results Broth-enriched PCR yielded a higher number of GBS-positive results than non-enriched PCR and culture (positive agreement 68.5% and 95.6%, respectively). At delivery, about 14% of GBS-carrying women were missed by antepartum PCR, while 7.7% received unnecessary intrapartum antibiotic prophylaxis due to loss of GBS colonisation (Cohen’s κ = 0.86). Kaplan-Meier analysis revealed GBS status retention > 95% until 3.7 weeks before delivery when antenatal PCR was used. Conclusion Broth-enriched PCR identified GBS colonization in a greater number of pregnant women than either broth-enriched culture or non-enriched PCR. A predictive window of 3.5 to 4 weeks before delivery (36–38 weeks of gestation) may optimise antepartum GBS PCR accuracy.