July 5, 2005 ROCHESTER, Minn. -- Mayo Clinic ear, nose and throat surgeons hoped to find a more user-friendly test for strep throat than swabbing the tonsils directly, but instead discovered that the swab has to touch the tonsils to accurately detect the infection.
"If we could have said that children don't have to have their tonsils swabbed -- that we could get the swab from the front of the mouth -- that would have been a good thing," says Laura Orvidas, M.D., Mayo Clinic ear, nose and throat surgeon and senior study investigator. "But, we're saying you can't do that."
Dr. Orvidas and colleagues conducted a study to determine if the tonsils infected with group A beta-hemolytic streptococci -- commonly known as strep throat -- shed enough DNA that the infection could be detected toward the front of the mouth. She explains that a certain amount of DNA is needed in order for a strep test to come out positive.
"We found you have to go all the way to the back of the throat to swab where there will be enough DNA -- you have to actually touch the tonsils," she says. "The infection is much more concentrated in the tonsil tissue."
The motivation for testing swabbing sites in the mouth other than the tonsils was to find a more child- and adult-friendly test, explain Dr. Orvidas and Jonathan Lee, M.D., Mayo Clinic ear, nose and throat surgical resident, who led the study.
"Tonsil swabbing is terrible -- it makes people gag," says Dr. Lee. "Children hate it."
Dr. Orvidas agrees. "With lots of children it's a struggle just to look in their throats, not to mention stick a swab back there," she says. "There are certain children for whom this is hugely traumatic. We're motivated to try to save them from 'the gag.'"
Dr. Orvidas explains that she's experienced the challenge of tonsil swabbing children not only with patients but also with her own daughter. "It was like I was killing her," she says of a recent occurrence.
The study was conducted prospectively with 130 patients undergoing tonsillectomy and in some cases, removal of the adenoids as well. Approximately three-fourths of the patients were children and one-fourth were adults.
During the surgery, the surgeons swabbed each patient's tonsil surface, the inside of the cheek by the back molars, and in between the lip and the gums in the front of the mouth. They also took tissue samples from the tonsil core and the adenoid, if an adenoidectomy was performed.
Dr. Lee analyzed the specimens for strep using two tests: standard culture and rapid cycle real-time polymerase chain reaction, technology that amplifies DNA. Strep was detected in one or more of the sampled sites in 41 cases; 29 of these were detected at the tonsil surface. Both testing methods were positive for strep in 28 of these 29 cases. In contrast, only 35 percent of those patients with strep on their tonsils were positive on the swab that came from between the lip and gum and in 43 percent of the cases where the swab was taken from the inside of the cheek.
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