Date Published: April 16, 2019
Publisher: Public Library of Science
Author(s): Trine Andreasen, Jens Kjølseth Møller, Mohammed Rohi Khalil, Anirudh K. Singh.
To 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.
This 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.
Ninety-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.
Both 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.
Group B streptococci (GBS) are the most frequent cause of early-onset neonatal infection, which is associated with significant morbidity and mortality among infants. The incidence rate of early-onset GBS infection ranges from 0.5 to 3.0 per 1,000 live births, with 4–10% mortality [1–4]. In their guidelines, Centers for Disease Control and Prevention (CDC) endorse universal culture-based antenatal screening for GBS colonization in all pregnant women between 35 and 37 weeks of gestation to identify women who should receive intrapartum antibiotic prophylaxis [1, 2]. However, 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 . 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.
This study was designed to compare the diagnostic accuracy of the BD MAX GBS assay and a new GenomEra GBS assay for rapid intrapartum PCR detection of vaginal carriage of group B streptococci using direct sample material from vaginal swabs. Based on a direct comparison with culture, BD MAX GBS had slightly better sensitivity, but lower specificity compared to GenomEra GBS, although the differences in performance were not statistically significant. Both PCR assays failed to detect GBS in all culture-positive vaginal samples, although they did detect GBS in several culture-negative specimens. Compared to a defined combined reference standard, there were no statistically significant differences between the respective performance characteristics of culture, BD MAX GBS PCR and GenomEra GBS PCR. The sensitivities of the three assays for detection of GBS in intrapartum vaginal ESwab samples were 83.0%, 87.3%, and 79.1%, respectively. Similar sensitivities were seen in a smaller study examining intrapartum GBS colonization status using GenomEra GBS PCR assay compared to culture .
Both PCR assays performed comparably to culture of the intrapartum vaginal samples. In particular, the GenomEra GBS PCR assay is potentially as an easy and rapid on-site test for intrapartum detection of vaginal carriage of GBS at a maternity ward to identify women in labor who should receive intrapartum antibiotic prophylaxis.