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Streptococcus Group B Antigen

The Food and Drug Administration (FDA) has issued a Safety Alert regarding the use of group B streptococcal (GBS) antigen detection. Antigen tests for GBS have produced false negative results in specimens from pregnant women and infants with subsequent infant deaths from GBS disease.

GBS antigen tests have also produced false positive results that may lead to inappropriate antibiotic therapy and prolonged hospitalization. Antigen tests are an adjunct to diagnosis. Multiple studies have shown that antigen tests are not an appropriate substitute for bacterial culture in the diagnosis of GBS colonization or infection. FDA suggested guidelines for use of antigen tests include:

Pregnant Women:

GBS antigen tests cannot be relied upon to exclude GBS colonization in a pregnant woman. Negative GBS antigen test results should be confirmed using selective broth culture which is more sensitive than antigen tests.


1. The only specimens recommended for GBS antigen testing are blood, serum, or cerebrospinal fluid. Testing infant urine is not recommended.

2. Antigen detection should not be used as a substitute for bacteriologic culture in the diagnosis of GBS septicemia or meningitis. A positive result indicates only the presence of GBS antigen, and not necessarily the presence of viable organisms. Positive or negative results should be considered presumptive and confirmed by culture.

The latest information on prevention of GBS disease is the consensus statement released by the Centers for Disease Control (CDC), American College of Obstetricians and Gynecologists, and American Academy of Pediatrics. Rapid antigen tests were not included in the protocol for detection or management of GBS.

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