Intrapartum tests for group B streptococcus: accuracy and acceptability of screening

Area of Science:

• Medical Diagnostics
• Microbiology
• Obstetrics and Gynecology

Background:

• Group B Streptococcus (GBS) poses a significant risk for neonatal infections.
• Current UK policy relies on risk factor-based screening for intrapartum GBS detection.
• Accurate and timely detection of maternal GBS colonization is crucial for preventing neonatal GBS disease.

Purpose of the Study:

• To evaluate the diagnostic accuracy of Polymerase Chain Reaction (PCR) and Optical Immunoassay (OIA) for detecting maternal GBS colonization during labor.
• To compare the performance of PCR and OIA against the established risk factor-based screening approach.
• To assess the acceptability of these novel testing methods among laboring women.

Main Methods:

• A diagnostic test accuracy study was conducted involving 1400 women in labor at two UK maternity units.
• Vaginal and rectal swabs were collected for PCR and OIA testing, with selective enriched culture serving as the reference standard.
• Participant acceptability was assessed via a post-delivery questionnaire, and factors influencing neonatal GBS colonization were analyzed using logistic regression.

Main Results:

• Maternal GBS colonization prevalence was 21% based on enriched culture.
• PCR demonstrated significantly higher sensitivity (84%) and specificity (87%) compared to OIA (72% sensitivity, 57% specificity) and risk factor screening (30% sensitivity, 80% specificity).
• Positive PCR results and maternal antibiotic use were strongly associated with neonatal GBS colonization, unlike traditional risk factors.

Conclusions:

• Intrapartum PCR screening is a highly accurate method for identifying maternal GBS colonization.
• PCR significantly outperforms OIA and risk factor-based screening in predicting both maternal and neonatal GBS colonization.
• The PCR test is well-accepted by women, offering a more effective screening strategy during labor.