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

We sought to evaluate an intrapartum nucleic acid amplification test (NAAT) for group B streptococcus (GBS).

This was a prospective cohort study of 559 women comparing intrapartum GBS culture with antepartum culture and intrapartum NAAT.

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.

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.