Evaluation of the Xpert Flu A Panel nucleic acid amplification-based point-of-care test for influenza A virus detection and pandemic H1 subtyping

Abstract

Background Influenza antigenic point-of-care (POC) tests are too insensitive for individual reliable diagnosis of influenza virus infections without additional laboratory confirmation. Molecular POC tests could be a valuable alternative. Objectives To evaluate the first influenza molecular POC test commercially available, the Cepheid Xpert Flu A Panel designed to simultaneously detect influenza A virus and subtype A(H1N1) 2009 pandemic virus, and compare it with in-house real-time RT-PCR (qRT-PCR). Study design Clinical specimens positive for influenza virus and influenza virus isolates with different viral loads and of different type and subtype were used to determine the analytical reactivity and sensitivity. A panel of pathogen negative specimens and isolates of 19 different respiratory pathogens were used to determine the analytical specificity. Results Except A(H9N2) virus the Xpert Flu A Panel detected A(H1N1) seasonal and 2009 pandemic, A(H3N2), A(H5N2), A(H5N1) and A(H7N7) viruses and correctly subtyped A(H1N1) 2009 virus. Analytical sensitivity was similar to qRT-PCR in the range of 400–5000 viral particles per ml. However, of most subtypes some specimens with cycle threshold values greater than 30 in qRT-PCR and A(H1N1) 2009 specimens with inconsistent results in the qRT-PCR due to primer or probe mismatches were not detected in the Xpert Flu A Panel. Analytical specificity was 100%. Conclusions The Xpert Flu A Panel is the first commercially available POC molecular test for detection of influenza A virus and determination of the H1 2009 subtype and is analytically reasonable sensitive compared with qRT-PCR and highly specific and therefore a welcome alternative to antigenic POC tests.