A method of performing a trend analysis on the concentration of influenza viral particles in a plurality of bodily fluid samples obtained from a subject, comprising: a) receiving in a reader assembly a cartridge, said cartridge containing a bodily fluid sample and comprising an immunoassay assembly, said immunoassay assembly containing a first immunoassay antibody reagent and a second immunoassay antibody reagent, and said reader assembly comprising a detection assembly; b) allowing said bodily fluid sample suspected of containing an influenza viral particle to react with said first immunoassay antibody reagent and said second immunoassay antibody reagent, wherein said first immunoassay antibody reagent comprises a first antibody that specifically binds to a hemagglutinin molecule present on an influenza viral particle to form a first immune complex on said influenza viral particle, and wherein said second immunoassay antibody reagent comprises a second antibody that specifically binds to a neuraminidase molecule also present on said influenza viral particle to form a second immune complex on said influenza viral particle, whereby said influenza viral particle is simultaneously bound by both said first immunoassay antibody reagent and said second immunoassay antibody reagent, said immune complexes yielding one or more detectable signals that indicate the simultaneous presence of hemagglutinin and neuraminidase on said influenza viral particle wherein either the first or second immunoassay reagent antibody is immobilized on a solid support; c) detecting, by said detection assembly or said reader assembly, said one or more detectable signals generated from said immune complexes, wherein said simultaneous presence of hemagglutinin and neuraminidase is indicative of the presence of and concentrations of said influenza viral particles in the sample; and d) repeating steps a), b) and c) for one or more further bodily fluid samples obtained from the subject over a period of time to detect concentrations of said analyte over said period of time, thereby performing said trend analysis wherein, said hemagglutinin is selected from the group consisting of H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15, and H16, and said neuraminidase is selected from the group consisting of N1, N2, N3, N4, and N5. a) receiving in a reader assembly a cartridge, said cartridge containing a bodily fluid sample and comprising an immunoassay assembly, said immunoassay assembly containing a first immunoassay antibody reagent and a second immunoassay antibody reagent, and said reader assembly comprising a detection assembly; b) allowing said bodily fluid sample suspected of containing an influenza viral particle to react with said first immunoassay antibody reagent and said second immunoassay antibody reagent, wherein said first immunoassay antibody reagent comprises a first antibody that specifically binds to a hemagglutinin molecule present on an influenza viral particle to form a first immune complex on said influenza viral particle, and wherein said second immunoassay antibody reagent comprises a second antibody that specifically binds to a neuraminidase molecule also present on said influenza viral particle to form a second immune complex on said influenza viral particle, whereby said influenza viral particle is simultaneously bound by both said first immunoassay antibody reagent and said second immunoassay antibody reagent, said immune complexes yielding one or more detectable signals that indicate the simultaneous presence of hemagglutinin and neuraminidase on said influenza viral particle wherein either the first or second immunoassay reagent antibody is immobilized on a solid support; c) detecting, by said detection assembly or said reader assembly, said one or more detectable signals generated from said immune complexes, wherein said simultaneous presence of hemagglutinin and neuraminidase is indicative of the presence of and concentrations of said influenza viral particles in the sample; and d) repeating steps a), b) and c) for one or more further bodily fluid samples obtained from the subject over a period of time to detect concentrations of said analyte over said period of time, thereby performing said trend analysis