Effectiveness of New Strep B Test

Newswise — Research at Michigan State University found that a new test that provides a quick and easy method for determining the presence of group B streptococcus, or GBS, in pregnant women is effective more than 90 percent of the time.

The research, which was headed by Dele Davies, chairperson of MSU's Department of Pediatrics and Human Development, is a lead article in the most recent issue of the scientific journal "Clinical Infectious Diseases."

The new molecular test, known as "real-time PCR," quickly detects the genes of the bacteria instead of relying on the bacteria to grow in a culture.

"It's our conclusion that this test is highly sensitive and specific," said Davies. "The results can be available in under two hours instead of the usual 48 hours for a culture. This means that in many clinics it can be used in labor-specific situations instead of cultures."

This can be very important for women who may have contracted GBS late in their pregnancy or had no prenatal care at all. According to guidelines from the Centers for Disease Control, pregnant women should be tested for GBS at 35 to 37 weeks of pregnancy.

Unfortunately, said Davies, many women may not be tested, while others could contract the disease between the time they are tested and the time they deliver the baby.

"This is very important for women who have had no prenatal care, or women whose results, for whatever reason, were lost," he said. "There is also a sub-set of women who deliver early and may not know the results of their tests."

In about half of cases, if a woman is carrying strep B, she will pass it along to her baby at the time of delivery unless she receives antibiotics.

Strep B can cause serious problems in newborns, including potentially fatal meningitis or pneumonia.

"Some of the symptoms can be fever, difficulty breathing and not feeding well," Davies said. "If they get strep in the blood, it can move to the brain and result in meningitis."

Today, due to increased testing and better diagnostic methods, less than one child in 1,000 gets the infection.

In their study, Davies and colleagues from five medical centers throughout North America compared the results of the standard culture test for GBS to the new molecular test.

In 94 percent of the more than 800 women that were evaluated, the molecular test was found to be at least comparable to the standard culture test.

"Use of this test during labor is highly sensitive and specific and may lead to a further reduction in rates of neonatal GBS disease," Davies said.

The only drawback to the molecular test, the researchers noted, is it is not able to determine if a certain strain of strep is resistant to antibiotics.