A sore throat, a brutal fever, a pounding head and a nasty cough – these symptoms all scream upper respiratory illness. But which one?
Many of the viruses that cause upper respiratory infections, such as influenza A or B and the virus that causes COVID-19, all use similar tactics. They target the same areas in your body – mainly the upper and lower respiratory tract – and this shared battlefield triggers a similar response from your immune system. Overlapping symptoms – fever, cough, fatigue, aches and pains – make it difficult to determine what the underlying cause may be.
Now, rapid tests at home can simultaneously determine whether someone has COVID-19 or the flu. Thanks in part to the National Institutes of Health’s Rapid Acceleration of Diagnostics (RADx) program, the Food and Drug Administration has granted emergency use authorization for seven rapid at-home tests that can distinguish between COVID-19, influenza A and influenza B.
Our team in Atlanta – including biomedical engineers, physicians and researchers from Emory University, Children’s Healthcare of Atlanta and Georgia Institute of Technology – is part of the RADx Test Verification Core. We work closely with other institutions and agencies to determine whether and how well COVID-19 and flu diagnostics work, ensuring effective testing. Our center has worked with nearly every COVID and flu diagnostic on the market, and our data has contributed to the instructions you’ll find in many of the at-home test kits on the market.
While no test is perfect, now being able to test for certain viruses at home when symptoms begin could help patients and their doctors come up with appropriate care plans more quickly.
A new era of home testing
Traditionally, identifying the virus causing upper respiratory symptoms required going to a clinic or hospital so that a trained medical professional could collect a nasopharyngeal sample. This involves placing a long fiber-tipped cotton swab, which looks like a skinny cotton swab, into one of your nostrils and all the way to the back of your nose and throat to collect virus-containing secretions. The sample is then typically sent to a laboratory for analysis, which can take hours to days for results.
Thanks to the COVID-19 pandemic, the possibility of using self-care tests to diagnose respiratory diseases at home became a reality. These tests used a much gentler and less invasive nasal swab and could also be performed by anyone, at any time, in their own home. However, these tests were intended to only diagnose COVID-19 and could not distinguish between other types of diseases.
Since then, researchers have developed over-the-counter multiplex tests that can screen for more than one respiratory infection at a time. In 2023, Pfizer’s Lucira test became the first at-home diagnostic test for both COVID-19 and influenza to receive emergency use authorization.
What are multiplex rapid tests?
There are two primary forms of combination testing for COVID-19 and COVID-19/flu at home: molecular tests such as PCR that detect genetic material from the virus, and antigen tests – commonly called rapid tests – which detect proteins called antigens. of the virus.
The majority of over-the-counter COVID-19 and COVID-19/flu tests on the market are antigen tests. They detect the presence of antigens in your nasal secretions that act as a biological signature for a specific virus. If viral antigens are present, it means you are probably infected.
To detect these antigens, rapid tests have paper-like strips coated with specially designed antibodies that function like a molecular Velcro and stick only to a specific antigen. Scientists design and manufacture specialized strips to recognize specific viral antigens, such as those from influenza A, influenza B or the virus that causes COVID-19.
The antibodies against these viral targets are placed on the strip, and when a person’s nasal sample contains viral proteins that are applied to the test strip, a line appears specifically for that virus.
Promote rapid antigen testing
Like all technologies, rapid antigen tests have their limitations.
Compared to laboratory-based PCR tests that can detect the presence of small amounts of pathogens by amplifying them, antigen tests are generally less sensitive than PCR and may miss an infection in some cases.
All home tests for COVID-19 and COVID-19/flu antigen are authorized for repeat use. This means that if someone is experiencing symptoms – or has been exposed to someone with COVID-19 but is not experiencing symptoms – and has a negative result on the first test, they should retest 48 hours later.
Another limitation of rapid antigen tests is that they are currently only designed to test for COVID-19, influenza A, and influenza B. Currently available over-the-counter tests are unable to detect disease from pathogens that resemble these viruses and similar symptoms, such as adenovirus or streptococci.
Because multiplexed texts can detect different viruses, they can also produce findings that are more complex to interpret than tests for individual viruses. This can increase the risk of a patient misinterpreting the results and misinterpreting one infection for another.
Researchers are actively developing even more advanced tests that are more sensitive and can simultaneously screen for a wider range of viruses or even bacterial infections. Scientists are also exploring the possibilities of using saliva samples in tests for bacterial or viral infections.
In addition, scientists are investigating the integration of multiplex tests with smartphones for rapid at-home diagnosis and reporting to healthcare providers. This may increase the accessibility of these tests for people with visual impairment, low dexterity, or other difficulties performing and interpreting tests at home.
Faster and more accurate diagnoses lead to more targeted and effective treatment plans, potentially reducing unnecessary antibiotic use and improving patient outcomes. The ability to quickly identify and track outbreaks can also allow public health officials to better limit the spread of infectious diseases.
This article is republished from The Conversation, an independent nonprofit organization providing facts and trusted analysis to help you understand our complex world. It was written by: Julie Sullivan, Emory University and Wilbur Lam, Georgian Institute of Technology
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Research conducted by ACME POCT was funded by the National Institutes of Health.
Wilbur Lam receives funding from the National Institutes of Health.