Ann Lab Med.  2013 Jan;33(1):39-44. 10.3343/alm.2013.33.1.39.

Usefulness of a Rapid Real-time PCR Assay in Prenatal Screening for Group B Streptococcus Colonization

• Park JS
• Cho DH
• Yang JH
• Kim MY
• Shin SM
• Kim EC
• Park SS
• Seong MW

• KMID: 1781296
• DOI: http://doi.org/10.3343/alm.2013.33.1.39

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.

Keyword

Streptococcus agalactiae; Prenatal diagnosis; Real-time PCR

MeSH Terms

DNA, Bacterial/*analysis
Female
Gestational Age
Humans
Pregnancy
Pregnancy Complications, Infectious/*diagnosis/microbiology
Prenatal Diagnosis
Reagent Kits, Diagnostic
Real-Time Polymerase Chain Reaction
Rectum/microbiology
Sensitivity and Specificity
Streptococcal Infections/*diagnosis/microbiology
Streptococcus agalactiae/*genetics/isolation & purification
Vagina/microbiology
DNA, Bacterial
Reagent Kits, Diagnostic

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