Rapid COVID-19 Tests: When to Use Them and How They Work

By December 2021, 200 million rapid tests are expected to be available to Americans each month as part of a drive to make community testing more widespread and accessible.

The announcement came last week with the White House signaling a billion-dollar investment in at-home rapid coronavirus tests.

It also said 20,000 pharmacies across the country would offer free testing starting from September.

We break down what these tests can do, the best times to do them, and list some of the most popular ones on the market.

Rapid tests for COVID-19 are a fast and easy method to detect the coronavirus. They are similar to a pregnancy test in the sense that they display one or two lines to indicate a result after a few minutes.

If the test detects viral antigens, which are a type of protein on the surface of the virus, it will show positive.

“Rapid tests are are a snapshot of how much virus you are shedding, if any,” said Eric Cioe-Peña, MD, director of global health at Northwell Health in New Hyde Park, New York.

He pointed out a caveat with these tests, it’s possible that if you have been exposed to COVID-19 the coronavirus could be building up in your body and eventually you will start to become contagious.

A negative result indicates that you likely do not have the infection at that moment in time.

“If the [result] is negative, it is usually pretty safe to engage in whatever event you are thinking about engaging in,” Cioe-Peña told Healthline.

If you present with COVID-19 symptoms, and want to see if you have the disease, rapid tests are quite reliable and can offer similar accuracy as polymerase chain reaction (PCR) tests processed in labs. StudiesTrusted Source have shown that antigen tests have comparable sensitivity to lab tests.

The current “gold standard” for clinically diagnosing COVID-19 is laboratory-based nucleic acid amplification tests (NAATs)Trusted Source. Loop-mediated isothermal amplification (LAMP) and PCR tests are the most commonly used NAAT techniques.

While both lab-based tests such as PCR and at-home rapid antigen tests detect a current infection, the former looks for viral ribonucleic acid (RNA) instead of viral antigens.

The sensitivity of rapid antigen tests can change depending on the course of infection and viral load. A higher viral load, which is usually a few days after infection, usually gives the most accurate results.

If rapid tests fail to detect enough antigens, they may produce a false negative. This can be because either the test was administered before symptoms appeared or the level of antigens was below the lowest limit the test could detect.

The advantages of rapid tests are that they are cheaper, take less time (compared to 1 or 2 days for PCRs), and are more widely accessible.

Covid test kitsCovid testsHow accurate are rapid antigen tests?Loop-mediated isothermal amplification (lamp)Polymerase chain reaction (pcr) testsRapid covid-19 tests: when to use them and how they workRapid tests for covid-19Test detects viral antigensWhat are rapid antigen tests?

Leave a comment

All comments are moderated before being published