Evaluation of a rapid, real-time intrapartum group B streptococcus assay

Objective We sought to evaluate an intrapartum nucleic acid amplification test (NAAT) for group B streptococcus (GBS). Study Design This was a prospective cohort study of 559 women comparing intrapartum GBS culture with antepartum culture and intrapartum NAAT. Results GBS prevalence was 19.5% by antepartum culture and 23.8% by intrapartum culture. Compared with intrapartum culture, antepartum culture had 69.2% sensitivity (60.6-76.9%) and 96.0% specificity (93.7-97.7%). The NAAT demonstrated sensitivity of 90.8% (84.6-95.2%), specificity of 97.6% (95.6-98.8%), and predictive values >92%. The incidence of discordant cultures was 10.4%. Of the women with negative antepartum and positive intrapartum cultures, only 1 (2.4%) received intrapartum antibiotics. Compared with white women, black ( P = .02) and Hispanic ( P = .02) women were more likely to have discordant cultures. Conclusion This intrapartum NAAT has excellent characteristics. It may be superior to antepartum culture for detecting intrapartum GBS–allowing more accurate management of laboring mothers and reducing neonatal GBS sepsis.