Rapid testing for group B streptococcus during labour: a test accuracy study with evaluation of acceptability and...

Area of Science:

• Obstetrics and Gynecology
• Infectious Diseases
• Medical Diagnostics

Background:

• Group B Streptococcus (GBS) colonization in pregnant women is a significant concern for neonatal health.
• Rapid diagnostic tests aim to improve intrapartum GBS screening efficiency.
• Current screening methods and rapid tests have varying accuracy and cost-effectiveness.

Purpose of the Study:

• To evaluate the accuracy, acceptability, and cost-effectiveness of Polymerase Chain Reaction (PCR) and Optical Immunoassay (OIA) rapid tests for detecting maternal GBS colonization during labor.
• To compare the performance of rapid tests with standard enriched culture methods.
• To assess the economic viability of different GBS screening strategies.

Main Methods:

• A test accuracy study was conducted in two UK obstetric units.
• Vaginal and rectal swabs were collected from women in labor for PCR and OIA testing.
• Results were compared against a reference standard of enriched culture.
• Participant and staff acceptability was assessed via questionnaires and focus groups.
• A decision-analytic model evaluated cost-effectiveness of various screening strategies.

Main Results:

• PCR demonstrated higher accuracy than OIA for GBS detection.
• Combined vaginal and rectal swabs yielded higher sensitivity for PCR compared to individual swabs.
• The sensitivity and specificity of rapid tests varied with maternal risk factors.
• PCR results, not maternal risk factors, predicted neonatal GBS colonization.
• Rapid testing acceptability was high among participants, though some ethnic groups showed lower satisfaction.
• Midwives expressed concerns about potential overtreatment.
• Routine intravenous antibiotic prophylaxis (IAP) for all women was the most cost-effective strategy, but screening with enriched culture was preferred if IAP was not implemented.
• Rapid test screening was not cost-effective at current performance levels.

Conclusions:

• Current rapid PCR and OIA tests are not sufficiently accurate for routine clinical use in GBS screening.
• Screening with enriched culture at 35-37 weeks gestation, followed by targeted IAP, appears to be the most acceptable and cost-effective strategy.
• Further evaluation is needed before implementing new GBS screening strategies.