Abstract
ObjectiveTo compare the diagnostic performance of BD MAX and GenomEra PCR assays for a rapid PCR detection of vaginal carriage of group B streptococci at delivery.MethodsThis is a retrospective laboratory analysis of vaginal swab samples taken intrapartum from a randomly selected cohort of pregnant women giving birth at a single childbirth and maternity unit.ResultsNinety-one culture-positive and 279 culture-negative vaginal samples were included from a cohort of 902 women. One-hundred-and-two specimens were found positive with the BD MAX and 84 with the GenomEra PCR assay. No statistically significant difference was observed compared to culture, sensitivity of BD MAX 84.6% (77/91) [95%CI 75.5–91.3] and of GenomEra 71.4% (65/91) [95%CI 61.0–80.4]. When compared to a combined reference standard, no statistically significant differences were seen between culture, BD MAX and GenomEra PCR assays. The sensitivities were 82.7% (91/110) [95%CI 74.3–89.3], 87.3% (96/110) [95%CI 79.6–92.9], and 79.1% (87/110) [95%CI 70.3–86.3], respectively.ConclusionBoth PCR assays performed comparably to culture of the intrapartum vaginal samples. In particular, the GenomEra assay is potentially an easy and rapid on-site PCR test for intrapartum detection of vaginal carriage of group B streptococci at a maternity ward to identify women who should receive intrapartum antibiotic prophylaxis.
Highlights
Group B streptococci (GBS) are the most frequent cause of early-onset neonatal infection, which is associated with significant morbidity and mortality among infants
A national cohort study found that samples for culture screening between week 35 and 37 of gestation were negative for 81% of the mothers of babies who developed early-onset neonatal group B streptococcal disease [5]
These data suggest that a change in colonization status may have occurred at the time of birth implying that antepartum sampling and culture are not optimal methods to provide a relevant GBS colonization status at delivery, resulting in missed opportunities to avoid GBS transmission from mother to infant during birth
Summary
Initial (first run of) PCR tests resulted in 102 positive samples with the BD MAX GBS and 84 with the GenomEra GBS assay (Table 1). The corresponding figures for the GenomEra GBS assay were 19 PCR positives of the 279 culture negative samples, and a specificity of about 93% (Table 2). Differences in sensitivity, specificity and predictive values between BD MAX and GenomEra with vaginal culture as the reference standard were not statistically significant (Table 2). Re-test results of vaginal intrapartum specimens with discordant first run results by BD MAX and GenomEra. Culture results and the combined reference standard are listed. Comparison of the statistical analysis of the culture, BD MAX GBS, and GenomEra GBS assay results compared with the combined reference standard.
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