Test For Strep Bacteria In Pregnant Women Misses More Cases Than Expected, Study Shows

Main Category: Pregnancy / Obstetrics
Also Included In: Medical Devices / Diagnostics
Article Date: 22 Jun 2009 - 4:00 PDT

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A federal recommendation that all pregnant women undergo testing for Group B strep bacteria has helped increase the number of screenings but also has produced a high level of false negatives, according to a study published Thursday in the New England Journal of Medicine, the AP/Newark Star-Ledger reports. Group B strep is a common bacteria in the intestines or lower genital tract. Although it poses no harm to most adults, during delivery it can be spread to infants, who can develop blood infections, pneumonia, meningitis, mental retardation, hearing and vision loss, or death. Problems occur in fewer than one in 3,000 births, but the Centers for Disease Control and Prevention in 2002 issued a recommendation that all pregnant women be tested because of the potential for serious complications. The study is the first research to examine the screening program. The researchers examined data on Group B strep cases in 10 states, finding that 250 infants out of nearly 7,700 were born with the infection. They compared the results with a similar study that was conducted before the CDC recommendations were in place, finding that the screening rate rose from 48% to 85% of pregnant women. The study also found that infant infections from Group B strep declined by 27%.

Researchers predicted there would be between 44 and 86 false negatives in full-term infants, based on data from previous studies. However, their results showed about 60% of infected infants -- 116 cases -- were born to women who had tested negative for Group B strep. Researchers noted that the timing of a Group B test might play a role because the infection can come quickly, and tests could have been performed before the bacteria appeared. CDC recommends that pregnant women be screened between 35 and 37 weeks' gestation. CDC researcher Stephanie Schrag, who co-authored the study, said, "Maybe it was a true negative test, and the mother later became colonized" with the bacteria before delivery (Stobbe, AP/Newark Star-Ledger, 6/17).

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