Background: Rapid diagnosis of GAS pharyngitis may improve patient care by ensuring that patients with GAS\r\npharyngitis are treated quickly and also avoiding unnecessary use of antibiotics in those without GAS infection.\r\nVery few molecular methods for detection of GAS in clinical throat swab specimens have been described.\r\nMethods: We performed a study of a laboratory-developed internally-controlled rapid Group A streptococcus\r\n(GAS) PCR assay using flocked swab throat specimens. We compared the GAS PCR assay to GAS culture results\r\nusing a collection of archived throat swab samples obtained during a study comparing the performance of\r\nconventional and flocked throat swabs.\r\nResults: The sensitivity of the GAS PCR assay as compared to the reference standard was 96.0% (95% CI 90.1% to\r\n98.4%), specificity 98.6% (95% CI 95.8% to 99.5%), positive predictive value (PPV) 96.9% (95% CI 91.4% to 99.0%) and\r\nnegative predictive value (NPV) of 98.1% (95% CI 95.2% to 99.2%). For conventional swab cultures, sensitivity was\r\n96.0% (95% CI 90.1% to 98.4%), specificity 100% (95% CI 98.2% to 100%), PPV 100%, (95% CI 96.1% to 100%) and\r\nNPV 98.1% (95% CI 95.2% to 99.3%)\r\nConclusions: In this retrospective study, the GAS PCR assay appeared to perform as well as conventional throat\r\nswab culture, the current standard of practice. Since the GAS PCR assay, including DNA extraction, can be\r\nperformed in approximately 1 hour, prospective studies of this assay are warranted to evaluate the clinical impact\r\nof the assay on management of patients with pharyngitis.
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