Comparison of rapid intrapartum screening methods for group B streptococcal vaginal colonization

To compare optical immunoassay (OIA) and rapid polymerase-chain reaction (PCR) with enrichment broth culture for intrapartum detection of vaginal group B streptococcal (GBS) colonization.

Paired vaginal swabs from 315 consecutive term pregnant women at the time of presentation for delivery to a university medical center were tested for GBS by OIA, PCR, and culture. Sensitivity, specificity, and positive and negative predictive values were calculated.

Vaginal colonization was identified by culture in 56 subjects (17.8%). The sensitivity of OIA (7.1%, 95% confidence interval 5.1-9.5%) was significantly less than that of unenhanced rapid PCR (62.5%, 95% CI 48.5-74.8%).

Neither PCR nor OIA is sufficiently sensitive for intrapartum detection of vaginal GBS colonization. Rapid PCR is more sensitive, but further improvements in technique to increase sensitivity will be necessary if PCR is to have a useful role in the management of women at time of presentation for delivery.