Evaluating the Accuracy of At-home Rapid Diagnostic Test Kits for Influenza

March 3, 2022

Over the past two years, discussions regarding the rapid rate at which respiratory viral infections (RVI) can be transmitted have escalated. While SARS-CoV-2 has certainly dominated the conversation, influenza remains a top concern. In an effort to learn more about reducing the spread of respiratory viruses, Evidation, alongside key partners, recently published a study in the Journal of Clinical Microbiology evaluating the diagnostic accuracy of the QuickVue Influenza A+B rapid diagnostic test (RDT) through self-reported, symptom-based testing triggers in an at-home setting.

"Working with Audere, the University of Washington, and with support from BARDA, Evidation was able to conduct one of the largest remote studies of influenza using at-home testing in order to capture the true everyday experience of the flu” mentioned Ernesto Ramirez, Senior Manager of Consumer Research at Evidation.

Approximately 5,229 individuals throughout the United States were recruited through the Evidation mobile app to partake in this research. Participants were sent “flu@home” test kits at the beginning of the study, and in the weeks that followed, were prompted to take daily symptom surveys within the mobile app. If participants reported experiencing cough along with aches, fever, chills, and/or sweats, they were instructed to use their flu@home test kit and indicate which results they saw on the RDT.

Of the 5,229 people who were sent test kits, 976 participants met the criteria to use theirs. Results showed that 202 (20.7%) individuals were positive for flu by qPCR. The RDT came back at 28% sensitivity and 99% specificity for Influenza A and 32% sensitivity and 99% specificity for Influenza B.

These results revealed three key takeaways that can help determine whether at-home RDTs have a place in the future of the healthcare industry. Jack Kotnik, Research Scientist at the University of Washington, commented on the results, saying, “It would be amazing to see this work be used as a foundation for evaluating at-home COVID-19 tests, and for other researchers to continue studying symptom-based prediction of respiratory illness and confirmatory testing with RDTs."

Early identification is key in determining RDT accuracy

Through this study, the research team came to the conclusion that early identification of individuals with respiratory symptoms using testing to confirm infection is key in managing RVI. Pre-positioning test kits and identifying influenza-like illness (ILI) through daily symptom surveys helped to minimize the time from the onset of particular symptoms to RDT use. 73% of participants who used the RDT did so within 24 hours of triggering it, and 51% did so within seven hours.

With that said, the QuickVue antigen-based RDT’s low sensitivity was similar to that found in other studies. This suggests that testing shortly after the onset of influenza-like symptoms that met trigger criteria did not improve the poor limit of detection of this test.

Both objective and subjective factors can affect rapid diagnostic testing results

When evaluating the results of this study, the researchers from Audere, University of Washington, and Evidation found that participants who reported the most symptoms and the greatest impact on their daily activities had lower Ct values and higher RDT sensitivity. Moreover, participants who reported they felt worse than when they are sick with a typical cold, as well as those who thought they were sick with influenza rather than a cold, were more likely to have influenza.

Based on this evidence, the team concluded that both objective presentation (i.e. number of symptoms) and a participant’s subjective perception of illness could 1) serve as effective guides for when to test and 2) provide additional confidence in test results.

Further research is needed to determine the best use of RDTs 

While the results of this study support the notion of app-supported, pre-positioned at-home RDT kits using symptom-based triggers, the QuickVue Influenza A+B RDT specifically cannot be recommended. Further research is required to determine ways to improve both the accuracy and efficacy of home-based influenza testing.

Despite being unable to recommend the RDT used in this particular study, experts believe that antigen-based immunochromatographic assays remain the most effective means to get diagnostics into at-home settings. With these tests playing a crucial role in the COVID-19 pandemic, it is imperative that the industry continues to explore all potential avenues in order to improve their performance. Says Ramirez, "This study is another example of harnessing the power of the Evidation community, our deep connection to our members, and our world class research and analysis expertise to better understand how we can use the power of individual data to fight infectious diseases."