Improvement of selection of pregnant women for intrapartum polymerase chain reaction screening for vaginal Group B Streptococci (GBS) colonization by adding GBS urine screening at 35-37 weeks of pregnancy

Objective To evaluate whether systematic antepartum screening for Group B Streptococci (GBS) by urine culture improves the risk factor-based selection of pregnant women for intrapartum GBS screening with a rapid polymerase chain reaction (PCR) assay. Methods A prospective observational study was conducted between April 2013 and June 2014. GBS colonization judged by urine culture at 35-37 weeks of gestation was compared with the result of a vaginal GBS PCR test at labor as outcome. The results of urine culture were used as exposure variable. The PCR test was performed on intrapartum vaginal samples. Results Screening for urine GBS in 902 unselected pregnant Danish women at 35-37 weeks of gestation predicted intrapartum PCR GBS status with a sensitivity of 33.6%. A positive predictive value of 41.2% was seen among women with low GBS counts (<104 CFU/mL) and 83.3% among women with high GBS counts (>= 104 CFU/mL). Systematic GBS screening of urine at 35-37 weeks of gestation added 30.9% extra women for intrapartum GBS PCR screening in the study group. Conclusion Systematic antepartum GBS screening of urine should be implemented in order to improve risk stratification for early onset GBS by offering laboring women an intrapartum GBS PCR test.