November 5, 2002

Franklin R. Cockerill, III, MD

This summer, the Mayo Clinic (Rochester, Minn.) began using a DNA-based strep A test that provides a confirmed result much more quickly than the previous algorithm of rapid antigen testing with culture confirmation of negative results. Antigen-based assays are among the more common forms of strep testing in physician office, clinics, and clinical laboratories, and these methods can give an initial result inside one hour. However, these tests fail to detect as many as 30% of strep cases, and culture confirmation of negative results may take up to 48 hours.

The new test, which was developed by researchers at the Mayo Clinic, uses rapid PCR technology to amplify the strep A DNA in a sample. Mayo studies have shown it to be as accurate as culture and significantly more accurate than the antigen test. In addition, it provides a confirmed result within eight hours, thereby eliminating the need to wait for culture confirmation.

According to Franklin Cockerill III, MD, the Mayo Clinic microbiologist who led the rapid DNA strep A development team, the new test will enable health-care providers to prescribe antibiotics on a more timely and accurate basis. "Using the antigen/culture method, many patients initially test negative for strep and therefore do not receive appropriate antibiotic treatment on the day of their office visit," said Cockerill.

This month, we are pleased to have Dr. Cockerill as our online expert. Dr. Cockerill’s presentation outlines the etiology, pathology, and symptoms of group A strep infection; current recommendations for diagnosis; a rationale for moving to rapid, DNA-based strep A diagnosis; Mayo’s evaluation of several commercially available antigen tests; and his appraisal of the new test.