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Rapid Tests Not Dependable for Detecting Novel Influenza A H1N1 Virus Print E-mail
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จันทร์, 10 สิงหาคม 2009

NEW YORK (Reuters Health) Aug 06 - Three models of rapid influenza diagnostic tests are relatively insensitive when testing for novel influenza A (H1N1) virus (swine influenza), particularly when viral titers in the clinical specimens are low, investigators report.

PDF download A. Balish and associates at the US Centers for Disease Control and Prevention compared results of rapid testing for influenza A viruses compared to original testing with real-time reverse transcription-polymerase chain reaction (standard test).Included were 45 specimens for novel influenza A (H1N1) virus (swine flu), five positive for seasonal influenza A (H1N1), and 15 for seasonal influenza A (H3N2).The three rapid tests were the Inverness Medical BinaxNOW Influenza A&B, the Becton Dickinson Directigen EZ Flu A+B, and the Quidel QuickVue Influenza A+B.For the nine specimens with high viral titers, one of the rapid tests had nine positive results, and the other two had eight positives, for a sensitivity of 89% to 100% in detection of the novel virus when compared with the standard test.However, for the 36 PCR-positive specimens with lower viral titers, the sensitivity of all three tests declined substantially. In addition, Balish and associates report, the 45 specimens that tested positive for the novel influenza A (H1H1) by rRT-PCR had a sensitivity on the three tests ranging from 40% to 69%.The test results were more accurate for the two seasonal influenza viruses.In a CDC editorial note, the investigators point out that that these rapid tests do not distinguish among influenza A virus subtypes, so test results should be interpreted in the context of currently circulating strains, level of clinical suspicion, severity of infection, and danger of complications."Conversely," they add, "a negative rapid influenza diagnostic test result should not be interpreted as indicating the absence of infection."To have specimens with the highest viral titer to increase test accuracy, they advise "optimizing specimen collection, transportation, and testing practices."In the event that a more definitive determination is needed, the editorialists recommend, "testing with real-time reverse transcription-polymerase chain reaction or virus isolation should be performed."Mor Mortal Wkly Rep CDC Surveill Summ 2009;58:826-829.Reuters Health Information © 2009 
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