title: Usefulness of a rapid real-time PCR assay in prenatal screening for group B streptococcus colonization.
abstract: BACKGROUND
  Group B streptococcus (GBS) infection is a leading cause of neonatal morbidity and mortality worldwide. Here, we present the analytical and diagnostic usefulness of a new real-time PCR-based assay (Xpert GBS; Cepheid, USA) for rapid and accurate prenatal GBS screening.
  
  
  METHODS
  We enrolled 175 pregnant women who were between 35 and 39 weeks of gestation. The analytical performance of the Xpert GBS assay was first tested using a reference GBS strain. Next, to test diagnostic performance, rectovaginal swabs were obtained from pregnant women who visited the hospital for regular antenatal screening after 34 weeks of gestation. The results of the Xpert GBS assay were compared to those of standard culture for the detection of prenatal GBS colonization.
  
  
  RESULTS
  When any positive result from Xpert GBS or culture was considered a true positive, the sensitivity of the Xpert GBS assay and culture were 91% (20/22; 95% CI [confidence interval], 72-98) and 68% (15/22; 95% CI, 47-84), respectively. The specificity of both methods was 100% (153/153; 95% CI, 97-100). The sensitivity and specificity of the Xpert GBS assay, using the culture results as a reference, were 86.7% and 95.6%, respectively. In the Xpert GBS assay, the median threshold cycle of vaginally colonized samples was significantly lower than rectally colonized samples (P<0.01).
  
  
  CONCLUSIONS
  The Xpert GBS assay is an accurate, rapid, easy-to-use test for the detection of maternal GBS colonization in prenatal screening that might be especially useful in clinical settings where standard culture is not feasible.
authors.affiliation: Department of Laboratory Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jeong Su
authors.initials: JS
authors.lastname: Park
authors.forename: Dong-Hee
authors.initials: DH
authors.lastname: Cho
authors.forename: Jae Hyug
authors.initials: JH
authors.lastname: Yang
authors.forename: Moon Young
authors.initials: MY
authors.lastname: Kim
authors.forename: Son Moon
authors.initials: SM
authors.lastname: Shin
authors.forename: Eui-Chong
authors.initials: EC
authors.lastname: Kim
authors.forename: Sung Sup
authors.initials: SS
authors.lastname: Park
authors.forename: Moon-Woo
authors.initials: MW
authors.lastname: Seong
mesh_terms: D004269:DNA, Bacterial / Q000032:analysis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis* / Q000382:microbiology; D011296:Prenatal Diagnosis; D011933:Reagent Kits, Diagnostic; D060888:Real-Time Polymerase Chain Reaction; D012007:Rectum / Q000382:microbiology; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000235:genetics* / Q000302:isolation & purification; D014621:Vagina / Q000382:microbiology
chemical_list: D004269:DNA, Bacterial; D011933:Reagent Kits, Diagnostic
keywords: Prenatal diagnosis; Real-time PCR; Streptococcus agalactiae