Comparison of two new generation influenza rapid diagnostic tests with instrument-based digital readout systems for influenza virus detection

Introduction: Influenza rapid diagnostic tests (RDTs) have been developed to supply scientists with more sensitive and specific techniques. Newly developed digital reader-based techniques require test evaluations before their clinical application. Methods: Two types of digital influenza RDTs using a digital readout system and one conventional RDT were compared using 314 nasopharyngeal swabs of influenza. The swabs originated from symptomatic individuals suspected of influenza infection, and the presence of influenza was confirmed with influenza real-time polymerase chain reaction (PCR) testing and influenza subtyping. Methods were the Sofia® Influenza A + B Fluorescence Immunoassay (FIA), which uses a portable fluorescence analyser, the BD Veritor™ System Flu A + B, which uses a colorimetric immunochromatographic method with a reflectance-based measurement digital device, and the SD Bioline assay, which is based on a traditional immunochromatographic method. Results: The Sofia® Influenza A + B system, the BD Veritor™ System Flu A + B and the SD Bioline assay showed sensitivities in relative real-time PCR results of 74.2, 73.0 and 53.9%, respectively, for influenza A, and 82.5, 72.8 and 71.0%, respectively, for influenza B. All three RDTs showed 100% specificities for influenza A and influenza B. The Sofia® Influenza A + B Fluorescence Immunoassay showed sensitive and specific results for the detection of influenza B in contrast to the BD Veritor™ System Flu A + B. The two digital RDTs showed higher sensitivity and specificity than the conventional RDT in the detection of the influenza H3 subtype. Conclusions: Digital-based readout systems for the detection of the influenza virus can be applied for more sensitive diagnosis in clinical settings than conventional RDTs.