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Performance of five FDA-approved rapid antigen tests in the detection of 2009 H1N1 influenza A virus


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Rapid antigen tests are commonly used by clinicians for rapid, simple, point-of-care testing. Five rapid antigen tests were shown to have low sensitivity (40.3–58.8%) when compared to real-time RT-PCR using nasal wash specimens from patients with influenza-like-illness (N = 167) that were collected previously and confirmed as 2009 pandemic influenza A (H1N1)-positive by PCR. Rapid antigen test sensitivity correlated with virus levels in nasal secretions when comparisons were made to cycle threshold (CT) values obtained from real-time RT-PCR. When CT values are <25 (equating to viral concentrations of >104 TCID50/ml) sensitivity for all five rapid antigen kits was high (range: 83–94% positive); however, when CT values are >30 (102 TCID50/ml), sensitivities of only 16–18% were observed for four of five rapid antigen kits. The Directigen EZ Flu A + B test detected more positive samples (35%) at lower viral concentrations with CT values >30 when compared with other commercial kits (P = 0.05). Rapid antigen test results must be interpreted with caution, and negative specimens may need confirmation by sensitive molecular assays. J. Med. Virol. 84:1699–1702, 2012. © 2012 Wiley Periodicals, Inc.