GBS Answers - Meridian Bioscience, Inc.

When It Comes to GBS
Testing, Ask for the Best
There was a time when losing newborns to Group
B Streptococcus (GBS) was not at all rare. In the
last few decades that has changed. Tragically, it still
happens, but not nearly as often as it used to. The
reason for the improvement? Routine diagnostic
GBS testing of pregnant women.
61.4%
Of term infants with
GBS disease were born
to women who had
tested negative for GBS
before delivery
(99.5% were tested with traditional culture)
Van Dyke, et al., NEJM, June 18, 2009; 360(25):2626-36
Approximately 90 percent of pregnant women who get prenatal care are now
being tested for Group B Strep. When a woman tests positive, she is treated
with IV antibiotics during delivery, preventing the transmission of bacteria
that is harmless in mom, but can be deadly to a newborn. That’s the good
news. The bad news is that laboratory tests aren’t perfect and can sometimes
return a negative result when the mother is actually a carrier of GBS. Studies
indicated that perhaps more than half of term infants born with GBS are born
to mothers who had tested negative for the bacterium.
The traditional method of testing for GBS is to take a vaginal swab from the
mother at 35 to 37 weeks in her pregnancy. This sample is cultured to give
the bacteria an opportunity to grow, and then examined to determine if GBS is
present. In this traditional method, there are many steps along the way where
mistakes can be introduced, explains Donna Mayne B.S (MT) ASCP, (CLS)
NCA, Molecular Lab Manager at Sacred Heart Hospital in Pensacola, Florida.
“Reading the culture is subjective and the bacteria can take two different
forms,” she says. “One is easy to see; the other is subtle.” The result is that
some women who should be testing positive for GBS are getting negative
results back from their tests.
“Accurate testing for GBS is so important,” explains Marti Perhach,
President and Founder of the Group B Strep International. “Otherwise,
moms who test negative are given false assurances that they don’t need
to be concerned about helping protect their baby from Group B Strep.
According to a 2009 Study in The New England Journal of Medicine,
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