Evaluation of a sensitive real-time PCR assay for Group B Streptococcus detection in vaginal-rectal swab.

Group B Streptococcus (GBS) is associated with invasive infections in newborns. The obstetric field requires a rapid method for obtaining GBS screening results. Our objective was to determine whether a sensitive real-time PCR assay demonstrates acceptable diagnostic performance. This study involved 301 pregnant women. Vaginal and rectal swabs were collected between 35 and 37 weeks of gestation. We report the diagnostic performance of the sensitive real-time PCR assay compared to composite reference method, along with 95% confidence intervals (CI). Positive results were detected in 35 cases (11.6%), 27 cases (8.9%), and 21 cases (6.9%), using real-time PCR, real-time PCR after enrichment, and microbial culture methods, respectively. Microbial culture and sequencing were applied as composite reference method, the sensitivity of real-time PCR was 96.15%, specificity was 96.36%, and diagnostic accuracy was 96.34%. Compared with the composite reference method, the sensitivity and specificity of the real-time PCR detection method after enrichment was 96.15% and 99.27%, with a diagnostic accuracy of 99.0%. Microbial culture demonstrated a sensitivity of 80.77%, specificity of 100%, and diagnostic accuracy of 98.33%. This study demonstrates that the sensitive real-time PCR assay represents an acceptable rapid GBS screening method, offering clinicians a new option for early screening.