Combination Influenza and COVID-19 Testing for Point-of-Care or At-Home Use
Advances in testing that were made during the COVID-19 pandemic have led to the development of improved tests for use at the point of care (POC) and at home, including combination tests for both influenza and COVID-19. With the cocirculation of influenza, COVID-19, and respiratory syncytial virus, the availability of accurate tests is greatly improving our ability to isolate when necessary and effectively treat our patients in a timely manner.
We know that polymerase chain reaction (PCR) testing offers a relatively high sensitivity and specificity, so, in the event of a positive test, the likelihood that a patient has the illness that is being tested for is much higher than it is with antigen testing. Much of the POC testing that is done in emergency departments, urgent care facilities, and hospitals is PCR testing. We can also now perform rapid POC PCR testing that provides results relatively quickly. It is still possible to perform antigen-based testing for influenza at the bedside, and I think that this is still a fairly good option for POC testing in a clinician’s office, where the proper lab equipment for PCR testing may not be available.
The relatively recent advancements in the availability of at-home testing have allowed families the ability to make decisions about their own care, as well as decisions about how to manage their interactions with people around them. That has been a significant change. We can now test at home and, upon analyzing those results, decide what to do in the event of a positive result (eg, follow up with a health care provider to discuss the appropriate use of antiviral treatments or other supportive therapy, as well as any potential prophylactic treatments for those within the household).
In many cases, for ambulatory patients with relatively mild illness, antiviral treatment might not be necessary, and this may be the case for both influenza and COVID-19. However, the option to treat is there if there is early testing and diagnosis, especially for individuals who have high-risk conditions that can make influenza or COVID-19 more dangerous. I think that this is where testing really can make a big difference. For older patients, patients with obesity, or patients with other underlying conditions that place them at a higher risk for developing severe disease, we know that early treatment can make a tremendous difference. So, I see a lot of benefit from the availability of at-home testing.
Another benefit of home-based testing for influenza and COVID-19 is that at-home testing can potentially help limit transmission by infected individuals. A positive test result at home can help families prevent further spread, both within and outside of the household. For influenza, especially, we know that starting antiviral treatment when appropriate and isolating infected family members can help prevent the further spread of the illness within the home. Moreover, a person who tests positive for influenza or COVID-19 can inform people outside the home (even those who have had casual exposure to the person who tested positive) about their potential exposure so that they can take necessary precautions. We cannot require social isolation as we did during the COVID-19 pandemic, so hand washing, wearing masks, and self-isolation if you test positive for an infection are important.
I am very happy that combined at-home testing for influenza and COVID-19 now exists. The optimal use of these tests and the evaluation of their results do require some understanding of the local circulation of these viruses. Following local or regional surveillance data will allow for a better understanding of the predictive value of the tests. When influenza or COVID-19 are actively circulating, testing negative with one of these tests means that you are likely to be truly negative, and testing positive means that you are likely to be truly positive. The performance of these at-home tests might be a bit different at the very early or late periods of circulation. PCR testing is more accurate and precise than antigen testing, and it is better to use PCR testing during periods when there is little viral circulation, such as at the beginning or tail end of the flu or COVID-19 season.
I think that the main issue is how the available at-home tests are being used. We know that at-home testing can be expensive, and sometimes tests are not readily available. Individuals should also be aware of their own level of potential exposure. If someone stays in their hometown and has limited potential exposures, their likelihood of being infected might be lower than someone who travels frequently or interacts with people who travel frequently. It is important to think of not only what is circulating in your own area but also people who come into your area from regions where influenza and COVID-19 are already highly active. While the use of at-home combination testing may be targeted to specific situations, having the option to test at home is wonderful.
Centers for Disease Control and Prevention. Ending isolation and precautions for people with COVID-19: interim guidance. Updated August 22, 2023. Accessed November 21, 2023. https://www.cdc.gov/coronavirus/2019-ncov/hcp/duration-isolation.html
Centers for Disease Control and Prevention. Overview of influenza testing methods. Reviewed August 31, 2020. Accessed November 21, 2023. https://www.cdc.gov/flu/professionals/diagnosis/overview-testing-methods.htm
Centers for Disease Control and Prevention. Overview of testing for SARS-CoV-2, the virus that causes COVID-19. Updated September 25, 2023. Accessed November 21, 2023. https://www.cdc.gov/coronavirus/2019-ncov/hcp/testing-overview.html
Christensen K, Ren H, Chen S, Cooper CK, Young S. Clinical evaluation of BD Veritor SARS-CoV-2 and flu A+B assay for point-of-care system. Microbiol Spect. 2022;10(2):e0180721. doi:10.1128/spectrum.01807-21
Larkin H. Combined COVID-19 and flu test authorized for emergency point-of-care use. JAMA. 2023;329(1):14-15. doi:10.1001/jama.2022.23890