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The skinny about at-home COVID-19 antigen tests

Jun 13, 2021 | Public Health

At-home COVID-19 antigen tests are now available in many stores. Get the facts on when and how they should be used.
We are now over a year into the pandemic and starting to see at-home COVID-19 infection antigen self-tests available for sale across our community. You may be wondering how these are different from tests you can get at the CBC-West testing site and why results are so much faster. And are they as reliable? Why would you pick this test over a test at a physician’s office or a test site? What can you do with this information?

The quick answer, it’s complicated. Let’s break it down.

Q: When should I test for COVID-19?
Test if you have symptoms of COVID-19 or have been exposed to someone with COVID-19 (within 6-feet of an infected individual for a cumulative 15 minutes over any 24-hour period OR have been directly in contact with infectious material (i.e. coughed or sneezed on). People should also test if it has been recommended by a medical provider, or if you need to know your COVID-19 status (i.e. for travel).

Q: What is a BinaxNOW test?
A: BinaxNOW tests have been available through the medical community for many months and are just now becoming available to the public for over-the-counter use. It’s an “antigen” test you can do at home; simply swab the inside of your nose, mix the stick with the included solvent and then wait around 15 minutes for a result.

Q: What is an antigen test?
A: An antigen is any foreign substance in the body that induces an immune response, especially the production of antibodies. A COVID-19 antigen test is used to detect infection with SARS-CoV-2. It is an “immunoassay” that detects the presence of the specific viral antigen for SARS-CoV-2 and is FDA authorized for testing symptomatic individuals in the test’s specified timeframe (usually the first 5-7 days of symptom onset). Results produce a yes/no result similar to a pregnancy test (one line = no infection, two lines = probable current infection). This is called a qualitative test, meaning it doesn’t give quantity of infection.

Q: What are its benefits and limitations?
A: They’re quick and affordable, offering symptomatic individuals answers of whether or not they are positive antigens of SARS-CoV-2 in around 15 to 30 minutes. This means the test-taker knows to isolate sooner, helping to prevent spread to others – especially those at high risk for serious health issues.

It does have its limitations, though. The test isn’t reliable for detecting virus in persons recently exposed who might be in the earlier stages of infection, before becoming symptomatic. This means they *are* infected just not at a stage where tests detect antigens. Because of this, tests may need to be repeated during someone’s quarantine period or if symptoms start showing up.
Here is a great website on viral tests:

Q: How does an antigen test differ from a molecular (PCR) test?
A: NAATs, such as real-time transcription-polymerase chain reaction (RT-PCR) are highly sensitive, highly specific tests for diagnosing SARS-CoV-2 infection. This test is detecting one or more viral ribonucleic acid (RNA) genes and specific to variants within that RNA profile. These tests can detect SARS-CoV-2 infection in folks with or without the usual symptoms. Its limitation exists in that it can also pick up previous infection, even if the individual was unaware they were infected. The same goes someone who has recently recovered from COVID-19. These tests are generally more expensive (except where currently offered at no cost) and the results can take 1-3 days.

Q: How can I use the positive/negative information given to me with an antigen test?
A: Currently, antigen tests are tracked as “probable” infections. A positive test should be considered as an active infection and can be followed up with a PCR test for confirmation. If followed up with a PCR test, make sure to wear a mask to the site to protect workers. A negative test is limited in that it represents only the individual’s antigen detectability at the time of the test – a snap shot in time.

Schools, work environments, and travel authorities may or may not accept negative antigen tests as confirmation of no current infection in individuals due to their probability of false negatives if tests are not done within the infection window. Check with these industries before assuming the test result will be accepted. More can be found at

So, what now?

If you are feeling cruddy, and you want to know if it’s COVID-19, a home antigen test is a good option. You can know to stay home and isolate (away from others including family) and notify your close contacts to quarantine (stay home, away from others and monitor for symptoms).

Remember these key tips:

  • Home tests are not tracked by public health, so contact tracing does not occur and it is not reflected in local case counts. Individuals with positive antigen tests are encouraged to get a PCR test so it can be anonymously registered with the state.
  • If anyone in your home tests positive for COVID-19, everybody living there is considered a “close contact”. At home, if in contact with sick individuals, your quarantine day 1 starts on the last day you are in contact with the contagious individual.
  • Quarantine means you stay home, away from others, for 14 days from exposure – or until you have received a negative test result for the shorter quarantine period (depending on your school district or what kind of work you do.)
  • Isolation means you stay home, away from others, including family members, until 10 days past the positive test and 24 hours without fever-reducing medications (but only if symptoms have improved.)
  • You will still need to follow testing guidelines as set for current travel requirements.

All of this and more can be found at:

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