Figuring out when and how to use an at-home COVID-19 test, or how to understand your results isn’t always simple. That’s because at-home COVID-19 tests — also known as rapid antigen tests — are not as accurate as the more reliable nasal swab PCR tests you can get at your doctor’s office. PCR stands for polymerase chain reaction.
The appeal of at-home COVID-19 tests is their convenience and accessibility. You can take the test at home (hence the name), and you can get a result within about 15 minutes. But it’s important to be cautious about rapid, at-home test results and how to use them. If you get a positive result, the test is likely accurate. If you get a negative result but are sick, you may still have COVID-19.
To help you understand what at-home COVID-19 tests are and how to interpret any results you get, we spoke with Dr. Michelle Barron, senior medical director of infection prevention and control for UCHealth and a professor of medicine and infectious diseases at the University of Colorado School of Medicine.
What is an at-home COVID-19 test?
The at-home tests detect proteins in the virus that causes COVID-19. These proteins are called antigens, and that’s why at-home rapid tests are known as antigen tests or rapid tests. They do not have to be sent to labs in order to get results. Usually, people can see their results in about 15 minutes. PCR tests, on the other hand, test for the genetic material of the active virus. The samples from these tests need to be analyzed in labs. That takes several hours and up to a couple of days, depending on how busy the labs are.
Are at-home COVID tests reliable?
At-home tests are accurate about 80% of the time. While 80% sounds decent for a grade on an algebra test, it’s not perfect for a COVID-19 test. It means that 20% of the time — or 1 in 5 times to drive the math home — when a person is infected with COVID-19, the test is not picking up evidence of the virus. This is known as a false negative result. And, if people use false negative results from rapid at-home tests incorrectly, they can endanger high-risk individuals like older adults, people with cancer or those with compromised immune systems.
That’s why Barron and other medical experts are urging people to be cautious about the tests.
Basic guidance about interpreting results from at-home COVID-19 tests:
Barron said this:
- Do not assume that a rapid, at-home test is accurate if you are feeling sick and you get a negative result.
- Do not assume that a rapid, at-home test is accurate if you have been in close contact with someone who has received a positive COVID-19 test result, and you are feeling sick. If you were in close contact with someone who tested positive for COVID-19, and you have any symptoms, it’s highly likely that you have COVID-19.
- Do assume that a positive result from an at-home test is accurate. If your rapid antigen test says you have COVID-19, you probably do. False positive results are not very common with at-home COVID-19 tests, Barron says.
“Use your common sense,” Barron said. “Do not use a negative result with an at-home test as a free pass to go out if you have symptoms. If you have a sore throat, a runny nose, a headache or any of the other symptoms of COVID-19 and you get a negative test result, you probably have COVID-19, and the test is missing it.”
Barron encourages people to continue using safety protocols that have worked since the pandemic began. If you feel sick, be conscientious and kind. If you have symptoms of an illness, whether you think it’s COVID-19, the flu or just a cold, stay home and don’t infect others. People who are sick should not show up at work, go to the gym, fly on a plane or attend a social gathering.
If I test positive for COVID-19 on an at-home test, is it likely that the result is correct?
Yes. A positive result on an at-home COVID-19 test is likely accurate.
If I test positive on an at-home COVID-19 test, do I need to get a PCR test to confirm the result?
No. If you test positive, you can assume you have COVID-19.
What should I do if I test positive using an at-home COVID-19 test?
- If you are experiencing any severe symptoms like difficulty breathing, call 911 immediately for help.
- If you don’t have severe symptoms, you should isolate yourself at home, stay hydrated and use over-the-counter medications if you need them.
- If you catch your infection early, call your doctor. You may receive a prescription for medication that can shorten the duration of your illness.
- If you are older, immunocompromised, pregnant or in another high-risk group, and you get a positive test result on an at-home test, contact your medical provider right away.
Why are there so many false negative results with at-home COVID-19 tests?
At-home COVID-19 tests produce a high percentage of false negative results because they are less sensitive than PCR tests. PCR tests are accurate nearly 99% of the time. Antigen tests don’t pick up all COVID-19 infections, but timing is also important. People sometimes test negative because they take the rapid at-home test too soon during the course of their illness. Or, it’s possible that they are not correctly swabbing themselves.
How do you take an at-home COVID-19 test?
Follow the instructions on your at-home test. Typically, at-home tests require people to swab their noses to get a sample. Do not share a single at-home test with others. The tests won’t work, and it’s unsanitary to use a single swab on multiple people.
Do at-home COVID-19 tests expire?
Yes. The rapid tests do expire. But some of the expiration dates have been extended. Check out additional information about expiration dates for at-home COVID-19 tests.
If you think you have COVID-19 or you were exposed to someone who got a positive test result, when should you take an at-home rapid COVID test?
- If you do not have symptoms, wait about five days before taking an at-home test.
- If you do have symptoms and you were exposed to someone with a confirmed case of COVID-19, you can assume you also have the illness since it’s contagious. If you are assuming you have COVID-19, isolate yourself so you don’t spread the illness.
“Wait at least 72 hours and ideally five days to get tested unless you have symptoms,” Barron said.
The reason she recommends waiting to take a test (unless you have symptoms) is that tests can’t immediately pick up COVID-19 infections.
“Say I had COVID-19, and I coughed on you. You’re not suddenly going to be positive in an hour. With some variants, the infection ramps up more quickly. But it’s not overnight. It still takes a couple of days,” Barron said.
If you have symptoms, you can go ahead and get a test or simply assume you have COVID-19 and behave accordingly.
“If you have symptoms, you are more likely to have COVID-19 than anything else,” Barron said.
Who should get COVID-19 tests?
People who are at high risk for suffering from severe consequences if they get COVID-19 should get tested. Other people may need to get tested for their jobs, school or before taking a trip.
People who are having medical procedures sometimes need to get a COVID-19 test.
People with common symptoms of COVID-19 may want to get tested. By now, the symptoms of the illness are quite familiar. They include the following: fever, shortness of breath, a new cough, fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting or diarrhea. Of course, these symptoms are also similar to the flu.
In general, if you are sick, stay home and don’t spread your illness to others. If you need to confirm whether or not you have COVID-19, use a rapid test or call your doctor’s office.
When might it make sense to use a rapid at-home COVID-19 test?
About five days after a person has been exposed to COVID-19 or if they have developed symptoms, it would make sense to get tested, preferably with a PCR test, Barron said.
What are the benefits of rapid, at-home COVID-19 tests?
One of the biggest potential benefits of rapid, at-home tests is accessibility, Barron said.
It’s much easier to stay home and take a test rather than go to a doctor’s office. At-home tests are also great for people who live in rural or remote areas.
Is it true that with an at-home test, you could test negative in the morning and positive later that same day?
Yes. All COVID-19 tests can only give results that amount to a snapshot in time.
That’s why it makes sense to wait to take a test either until you have symptoms or until about five days after you’ve been exposed to someone who has tested positive for COVID-19. Taking a test immediately after exposure doesn’t do much good.
“You’re just trying to reassure yourself without actually reassuring yourself,” Barron said.