Semi-quantitative analysis of influenza samples using the Luminex xTAG® respiratory viral panel kit

The Luminex xTAG (R) respiratory viral panel (RVP) kit simultaneously detects and identifies multiple respiratory viruses including several subtypes of influenza A using a multiplex nucleic acid amplification test assay platform. The emitted fluorescence signal from the RVP assay provides qualitative information on the presence of a particular viral species in respiratory specimens. However, a quantitative assessment is preferred when monitoring environmental samples for respiratory viruses. In this study, we explored the potential use of the RVP kit as a semi-quantitative screening assay for influenza virus detection. The concentration-response of the RVP assay was modeled using four-parameter logistic (4-PL) fits of mean fluorescence intensity (MFI) versus dilute ranges of the influenza A matrix gene, seasonal influenza vaccine, and 2009 H1N1 influenza vaccine. The goodness of fit of the 4-PL model was evaluated by comparing the copy number determined with the fitted model (observed copy number) with the copy number calculated from the dilution of the matrix DNA or vaccine (expected copy number). For the matrix DNA and 2009 H1N1 vaccine, the 4-PL model provided good fit for the influenza A RVP assay response over factors of 10(3) to 10(4). For seasonal influenza vaccine, the model provided good fit for RVP assay response to influenza A, influenza B, H1, and H3.