A new type of test under development could provide another way to identify people actively infected with the novel coronavirus. Like the diagnostic tests already in use— known as PCR tests— these new tests would spot the virus itself. They would detect protein molecules called antigens that sit on the surface of the virus.
The technology for COVID-19 antigen tests has been around for years. It's the same that's used in rapid strep and flu tests. These tests would be equipped with another kind of protein—an antibody— that would recognize and bind to the coronavirus antigens. So, from nasal swab to test result would take just a few minutes. The COVID-19 antigen tests would be much simpler to make and operate than PCR tests.
They also would be easier to scale up and offer widely. But experience with other rapid antigen tests suggests tests probably won’t be as accurate as PCR. This is because PCR finds and makes many copies of the virus’s genetic material so that it’s more detectible. In contrast, COVID-19 antigen tests would either find the virus as it is or not. In other words, no amplification is performed. Fine-tuning these tests will be tricky. They should be accurate enough to pick-up only COVID-19 antigens without recognizing antigens from other coronaviruses found in the common cold. This means COVID-19 antigen tests probably will miss some people who have the virus and incorrectly tell others they do have it.
How well these tests might work will depend on factors like how long the person has been infected, the amount of virus in the sample, the quality of the sample and how it’s processed, and also the make-up of the materials used to run the test—known as reagents. Even with these limitations, COVID-19 antigen tests may be used to screen people likely infected with the virus, especially when having a quick yes or no answer matters the most.
The technology for COVID-19 antigen tests has been around for years. It's the same that's used in rapid strep and flu tests. These tests would be equipped with another kind of protein—an antibody— that would recognize and bind to the coronavirus antigens. So, from nasal swab to test result would take just a few minutes. The COVID-19 antigen tests would be much simpler to make and operate than PCR tests.
They also would be easier to scale up and offer widely. But experience with other rapid antigen tests suggests tests probably won’t be as accurate as PCR. This is because PCR finds and makes many copies of the virus’s genetic material so that it’s more detectible. In contrast, COVID-19 antigen tests would either find the virus as it is or not. In other words, no amplification is performed. Fine-tuning these tests will be tricky. They should be accurate enough to pick-up only COVID-19 antigens without recognizing antigens from other coronaviruses found in the common cold. This means COVID-19 antigen tests probably will miss some people who have the virus and incorrectly tell others they do have it.
How well these tests might work will depend on factors like how long the person has been infected, the amount of virus in the sample, the quality of the sample and how it’s processed, and also the make-up of the materials used to run the test—known as reagents. Even with these limitations, COVID-19 antigen tests may be used to screen people likely infected with the virus, especially when having a quick yes or no answer matters the most.
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