Objective: The objectives were to evaluate and compare the diagnostic accuracy of a rapid real-time PCR assay at the onset of labor with those of the current antenatal culture-based test at 34-38 weeks gestation for group B Streptococcus (GBS) screening.

Methods: A prospective study including all pregnant women admitted for delivery after a 34-week gestation period was conducted in October 2012 at the Grenoble University Hospital Centre. A first culture-based GBS screening test was performed between 34 and 38 weeks of gestation followed by a second screening test at the onset of labor, using a real-time PCR Assay and a culture-based method (gold standard) in order to calculate the diagnostic accuracy.

Results: One hundred an fifty-seven patients were enrolled. The sensitivity was 94.4% (95% CI, 72.7-99.9%) with intrapartum PCR assay and 50% (95% CI, 26-74%) with antepartum culture. Prevalence of GBS colonization was 7.6% with the antepartum culture method, 11.5% with intrapartum culture and 16.6% by using PCR-test.

Conclusions: Intrapartum PCR shows a much higher sensitivity compared to the antepartum culture-based screening mainly due to variations in GBS colonization and could allow us to target patients requiring intrapartum antibiotic prophylaxis more effectively.