Many women are having different test results for Group B streptococcus (GBS) between their routine third trimester screening

"Most women are currently screened for GBS in their last trimester, but even if the test is negative, GBS can still develop before women give birth," said Brett Young, M.D, an obstetrician undergoing training in high risk obstetrics at Massachusetts General Hospital. "We know that two-thirds of infants with GBS sepsis are born to mothers with negative third-trimester cultures, so we wanted to see how many women with a negative GBS test in the third trimester have a positive GBS result right before delivery. These babies in particular are at risk for acquiring GBS infection because the mothers are not given appropriate antibiotics in labor."
Young and her colleagues enrolled women in their study who presented to labor and delivery with an antepartum GBS culture. GBS cultures and rapid tests were performed during labor and compared to the third trimester GBS culture results
Among 559 women, GBS prevalence was 19.5% with the third-trimester culture and 23.8% with culture performed on samples collected during labor. Compared with the culture obtained during labor, the third-trimester culture correctly predicted GBS positivity at the time of labor only 69% of the time versus the rapid test which correctly predicted GBS positivity 91% of the time. The incidence of GBS discordance from the late third trimester to labor was 10%. Compared with women who identified as Caucasian, African-American and Hispanic women were significantly more likely to have discordant culture results.
The study found that the rapid GBS test used when women present in labor has excellent test characteristics and may be a useful adjunct to the third trimester culture for accurately detecting the presence of GBS at the time of labor.
"We found that African-American and Hispanic women were significantly more likely to have results that converted from the third trimester to the time of labor, so the use of the rapid test might be even more beneficial in those groups," said Young.
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Source-Eurekalert