TRI: No Shortcut to Strep Test - CME Teaching Brief - MedPage Today
TRI: No Shortcut to Strep Test - CME Teaching Brief - MedPage Today: "TRI: No Shortcut to Strep Test
By Katrina Woznicki, MedPage Today Staff Writer
Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of Pennsylvania School of Medicine.
May 15, 2005
MedPage Today Action Points
* Physicians will still have to swab the tonsils to get the most accurate results for Group A Beta-Hemolytic Streptococci. Swabbing the cheek or gums was not as effective.
* Rapid cycle real time polymerase chain reaction (RT-PCR) testing was superior to standard culture testing in detecting Streptococci from tonsil core and adenoid tissue specimens.
* This study was published as an abstract and presented at a conference either as an oral or poster presentation. These data and conclusions should be considered to be preliminary as they have not yet been reviewed and published in a peer-reviewed publication.
Review
BOCA RATON, Fla.- They tried the cheek and they tried the gums, but in the end they needed to swab the tonsils for enough DNA for an accurate diagnosis of Group A Beta-Hemolytic Streptococci.
So reported a Mayo Clinic group that had sought a more user-friendly DNA-based strep test. Instead, the investigators said Sunday at the Triological Society meeting here, only direct swabbing of the tonsils yielded the most accurate results, even with a rapid cycle real-time polymerase chain reaction (RT-PCS) assay.
'We found you have to go all the way to the back of the throat to swab where there will be enough DNA,' said Laura Orvidas, M.D., an otorhinolaryngologist at the Rochester, Minn., facility. 'You have to actually touch the tonsils. The infection is much more concentrated in the tonsil tissue.'
The Mayo group conducted a prospective study of 130 patients, about 75% of them children, all undergoing tonsillectomy. Some were also having an adenoidectomy.
The researchers used two tests, standard culture and rapid cycle RT-PCS, which takes only hours, not days, to produce results. They swabbed from the tonsil surface, in front of the mouth between the lip and gum, and inside the cheek towards the back molars. Tissue samples were also collected from the tonsil core and from the adenoid tissue among patients undergoing adenoidectomy.
In 41 of the patients, Streptococcus was detected from one or more of the swabbed sites, and 29 of those positive results were detected on the tonsil surface. Standard culture and rapid cycle RT-PCR techniques were both positive for strep in 28 of the 29.
Neither test showed significant superiority in the analysis of gum and cheek swabs. Of the 29 strep cases, standard and RT-PCR tests were both positive at the lip-gum site from four cases. Of seven tonsil surface positive cases that also had interior cheek swabs, RT-PCR was only positive for one case and standard culture was positive for two.
The detection rates from inside the cheek or at the gum were lower than those taken from the tonsil surface no matter which test was used. Only 43% of patients with strep on their tonsils were positive from the swab that was taken from the interior of their cheek. That figure dropped to 35% of patients where the swab was taken from between the lip and gum.
The researchers also found RT-PCR was superior to standard culture in detecting Group A Beta-Hemolytic Streptococci from the tonsil core and adenoid tissue samples. The RT-PCR test detected the bacteria in 11 tonsil core samples and from 10 adenoid tissue specimens whereas the standard culture test failed to do so.
Primary source: Triological Society Annual Meeting
Source reference:
Lee at al, Rapid Cycle Real Time PCR Versus Standard Culture Detection of Group A Beta-Hemolytic Streptococci at Various Anatomical Sites in Tonsillectomy Patients, Triological Society Annual Meeting, May 13-16, 2005, Boca Raton, Fla."
By Katrina Woznicki, MedPage Today Staff Writer
Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of Pennsylvania School of Medicine.
May 15, 2005
MedPage Today Action Points
* Physicians will still have to swab the tonsils to get the most accurate results for Group A Beta-Hemolytic Streptococci. Swabbing the cheek or gums was not as effective.
* Rapid cycle real time polymerase chain reaction (RT-PCR) testing was superior to standard culture testing in detecting Streptococci from tonsil core and adenoid tissue specimens.
* This study was published as an abstract and presented at a conference either as an oral or poster presentation. These data and conclusions should be considered to be preliminary as they have not yet been reviewed and published in a peer-reviewed publication.
Review
BOCA RATON, Fla.- They tried the cheek and they tried the gums, but in the end they needed to swab the tonsils for enough DNA for an accurate diagnosis of Group A Beta-Hemolytic Streptococci.
So reported a Mayo Clinic group that had sought a more user-friendly DNA-based strep test. Instead, the investigators said Sunday at the Triological Society meeting here, only direct swabbing of the tonsils yielded the most accurate results, even with a rapid cycle real-time polymerase chain reaction (RT-PCS) assay.
'We found you have to go all the way to the back of the throat to swab where there will be enough DNA,' said Laura Orvidas, M.D., an otorhinolaryngologist at the Rochester, Minn., facility. 'You have to actually touch the tonsils. The infection is much more concentrated in the tonsil tissue.'
The Mayo group conducted a prospective study of 130 patients, about 75% of them children, all undergoing tonsillectomy. Some were also having an adenoidectomy.
The researchers used two tests, standard culture and rapid cycle RT-PCS, which takes only hours, not days, to produce results. They swabbed from the tonsil surface, in front of the mouth between the lip and gum, and inside the cheek towards the back molars. Tissue samples were also collected from the tonsil core and from the adenoid tissue among patients undergoing adenoidectomy.
In 41 of the patients, Streptococcus was detected from one or more of the swabbed sites, and 29 of those positive results were detected on the tonsil surface. Standard culture and rapid cycle RT-PCR techniques were both positive for strep in 28 of the 29.
Neither test showed significant superiority in the analysis of gum and cheek swabs. Of the 29 strep cases, standard and RT-PCR tests were both positive at the lip-gum site from four cases. Of seven tonsil surface positive cases that also had interior cheek swabs, RT-PCR was only positive for one case and standard culture was positive for two.
The detection rates from inside the cheek or at the gum were lower than those taken from the tonsil surface no matter which test was used. Only 43% of patients with strep on their tonsils were positive from the swab that was taken from the interior of their cheek. That figure dropped to 35% of patients where the swab was taken from between the lip and gum.
The researchers also found RT-PCR was superior to standard culture in detecting Group A Beta-Hemolytic Streptococci from the tonsil core and adenoid tissue samples. The RT-PCR test detected the bacteria in 11 tonsil core samples and from 10 adenoid tissue specimens whereas the standard culture test failed to do so.
Primary source: Triological Society Annual Meeting
Source reference:
Lee at al, Rapid Cycle Real Time PCR Versus Standard Culture Detection of Group A Beta-Hemolytic Streptococci at Various Anatomical Sites in Tonsillectomy Patients, Triological Society Annual Meeting, May 13-16, 2005, Boca Raton, Fla."
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