Group B streptococcus (GBS) early-onset sepsis is a leading cause of neonatal morbidity and mortality. Two-thirds of infants with GBS sepsis are born to mothers with a negative third-trimester GBS culture—the current screening test. Given the transient nature of GBS colonization we evaluated the test characteristics of a rapid intrapartum GBS test and the current screening test along with the incidence of GBS conversion from the third trimester to intrapartum.
Women presenting to labor and delivery with an antepartum GBS culture were enrolled. Intrapartum recto-vaginal samples were obtained per CDC guidelines for the culture and rapid test. The intrapartum culture was the gold standard to calculate test characteristics and 95% confidence intervals.
Among 559 women who delivered 563 neonates, GBS prevalence was 19.5% with antepartum culture and 23.8% with intrapartum culture. Compared with intrapartum culture, antepartum culture had sensitivity of 69.2% (60.6-76.9) and specificity of 96.0% (93.7–97.7). The rapid intrapartum test showed sensitivity of 90.8% (84.6–95.2), specificity of 97.6% (95.7–98.9), positive predictive value of 92.3% (86.2–96.2) and negative predictive value of 97.2% (95.1–98.5). The incidence of GBS conversion from the late third trimester to labor was 10.4%. The time interval between the antepartum and intrapartum tests was the same for women who did not convert as for those who converted (P=0.99). Compared with women who identified as Caucasian, African-American (P=0.02) and Hispanic (P=0.02) women were significantly more likely to convert. The incidence of neonatal blood culture was 35% among women who converted to negative versus 17% among women who remained negative.
This intrapartum rapid GBS test has excellent test characteristics and may be superior to the antepartum culture for accurately detecting intrapartum GBS colonization. Use of this rapid intrapartum test may improve the precision of neonatal sepsis evaluations, and may thus impact the incidence of neonatal GBS sepsis.
© 2011 Mosby, Inc. Published by Elsevier Inc. All rights reserved.