September 10, 2014
2 min read

Molecular tests accurately diagnosed GAS pharyngitis

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Rapid antigen diagnostic tests, such as molecular tests, can be used to streamline management of sore throat in primary care based on recent data that show they had good sensitivity and specificity when diagnosing group A streptococcal pharyngitis.

Wei Ling Lean, MBBS, BMedSc, of Royal Children’s Hospital in Melbourne, Australia, and colleagues reviewed data from 48 studies on diagnostic accuracy of group A streptococcal (GAS) pharyngitis rapid antigen diagnostic tests. Selected studies used throat culture on blood agar as a reference standard and were published from 1996 to 2013. Data was available for 23,934 patients.

Overall, rapid antigen diagnostic tests had an estimated sensitivity of 0.86 (95% CI, 0.83-0.88) and specificity of 0.96 (95% CI, 0.94-0.97). Sensitivity varied considerably, but there was little variability in specificity, according to researchers.

Diagnostic tests in the molecular technique category had the best performance, with a pooled sensitivity of 0.92 (95% CI, 0.89-0.95) and specificity of 0.99 (95% CI, 0.97-0.99). The other test categories, lateral flow/immunochromatographic assay and optical immunoassay, had comparable pooled sensitivities and specificities, ranging from 0.84 to 0.86 and 0.94 to 0.96, respectively.

Molecular techniques performed better in a pediatric population compared with optical immunoassay and lateral flow/immunochromatographic assay; and had a sensitivity of 0.93 (95% CI, 0.89-0.96) and a specificity of 0.99 (95% CI, 0.98-1). Both optical immunoassay and lateral flow/immunochromatographic assay had a sensitivity of 0.85 (95% CI, 0.8-0.89). Optical immunoassay had a specificity of 0.95 (95% CI, 0.93-0.97) and lateral flow/immunochromatographic assay had a specificity of 0.97 (95% CI, 0.95-0.98).

“The diagnostic accuracy of the more recently developed rapid antigen diagnostic tests (molecular techniques) is encouraging,” the researchers wrote.

However, there are drawbacks to diagnostic tests that use molecular-based techniques, according to researchers. They are not truly “point-of-care” tests because they have a longer turnaround time between 1 and 3 hours vs. immune-based tests that have a turnaround time as low as 30 seconds.

“Further research could focus on improving the practicality of these tests, especially when they are used in the primary care setting,” the researchers concluded.

Disclosure: Two researchers received funding for a previous study of a Quidel Corporation rapid antigen diagnostic test product. The other researchers report no relevant financial disclosures.