Streptococcus Group B antepartum culture screening vs. intrapartum PCR rapid test: A meta analysis

Streptococcus agalacticae (Group B Streptococcus, GBS) is a main pathogen causing early onset disease (EOD) in neonates. GBS positive mothers receive intrapartum antibiotics (IAP) to prevent newborns from EOD. The GBS screening in pregnant mothers is often performed via culture swab testing during the 3rd trimester (aCulture), or with an intrapartum commercial real-time polymerase chain reaction assay (iPCR). The aim of this study was to analyze the diagnostic accuracy of the aCulture (gold standard) and iPCR for GBS colonization in pregnant women and conclude implications for clinical practice.
The systematic literature search was conducted on PubMed, Cochrane and Livivo, initially in April 2024 and repeated in February 2025. Studies with publication date between 2012 and 2025 were included if they compared the diagnostic accuracy of aCulture and iPCR (Xpert Xpress GBS) to intrapartum culture as reference standard. All study participants were required to have completed all three tests before inclusion in the analysis. Studies underwent critical appraisal using QUADAS-2 and QUADAS-C. To account for the tradeoff between sensitivity and specificity, we conducted a meta-analysis of diagnostic test accuracy by fitting a bivariate random-effects model to the true positive and false positive rates. In addition, we fitted univariate random-effects models for diagnostic odds ratio (DOR), likelihood ratio of a positive (LR + ) and negative test (LR-), respectively. Models were fitted using the `mada` package in R. Four studies were included with a total of 3052 participants (1–4).
For aCulture screening, pooled diagnostic performance was as follows (estimate and 95% CI): Sensitivity (Sn) 0.82 (0.58-0.94), specificity (Sp) 0.97 (0.96-0.98), DOR 140.43 (CI: 62.15-317.27), LR+24.03 (CI: 19.31-29.90) and LR- 0.20 (0.08-0.52). For the iPCR the pooled accuracy was Sn 0.93 (0.90-0.95), Sp 0.97 (0.94-0.99), DOR 661.19 (432.11-1011.71), LR+31.48 (13.72-72.20) and LR- 0.09 (0.07-0.11).
Both tests met the 95% specificity threshold, but aCulture fell short of the 90% sensitivity requirement. iPCR showed a significantly lower LR−, indicating better ability to rule out GBS. Consequently, iPCR demonstrates superior diagnostic accuracy and greater prophylactic value in managing IAP to reduce vertical GBS transmission during labor. Its timely bed-side results support more precise antibiotic use, potentially lowering antimicrobial resistance. However, the lack of susceptibility testing limits a full shift from antenatal culture to iPCR screening. A combined approach may be feasible, with iPCR as the standard and aCulture especially for patients with antibiotic allergies.