COVID Tests: From Rapid Home Tests to PCR, Here’s What You Need To Know Right Now


You can therefore test negative on a home test even if you are infected – at the beginning or at the end of your illness, for example, when you do not have many viruses.

The most pressing question, says Butler-Wu, is, “What test can you get?

If you’re showing symptoms and have likely been exposed to the virus while traveling or socializing, a positive antigen test is probably sufficient proof that you have the virus, says Dr Abraar Karan, an infectious disease physician at Stanford University.

As for PCR testing, availability depends on demand in your community. Some testing facilities are criticized, with few appointments available and waiting hours even though you can land an appointment. And it may take several days to get the results of a PCR test.

When should I test?

The answer depends on whether you can take a test – and how you use it. A test can be used to tell you if you have COVID-19 – for example, if you are showing symptoms or if you’ve been around someone who tested positive. And they can also be used as an added precaution before socializing (which we’ll discuss a few questions below).

If you’ve been exposed to someone with COVID-19, you should test yourself. But not right now.

“If you’ve been exposed, wait a few days because the immediate tests could be negative,” Karan explains. After waiting, “then we will be able to detect the virus”.

The Centers for Disease Control and Prevention recommends self-testing either when symptoms develop or, if you do not have symptoms, five to seven days after exposure. This would give the body enough time to develop a viral load that could be detected by a home test.

With the omicron variant, rapid tests have been reported to be negative in the first day or two of the first symptoms. So even if you have symptoms, you may want to wait a day or two for the first test, especially if you have a limited number of tests.

A rapid COVID-19 test hosted by a healthcare professional at a Unidos En Salud test site, a collaboration between UCSF and the Latino Task Force, at a COVID-19 awareness event after the holidays on the 24th. and Mission Streets in San Francisco on November 30, 2020. (Beth LaBerge / KQED)

How many tests do I have to take?

At least two.

Why test twice? Home tests are most accurate when you use them in series – at least two in a few days. And if you have a limited number of home tests, you’ll want to aim for when you’re most likely to get an accurate result, such as days 5 and 7 after exposure.

“These tests absolutely have to be used in series, to be perfectly honest. They don’t have the sensitivity to be used individually if they are negative,” says Butler-Wu. “By repeating it, you allow the virus to potentially grow larger to the point, in essence, where you can now detect it.”

“If that test is negative, all you tell you is, at this point you don’t have a ton of virus in you,” Karan says.

Should I get tested before I see people?

“If you’re going to visit Grandma or something, yes, I would probably do a quick test before that,” Karan says. “Or if I go somewhere where it is going to be a lot of people. If I am contagious that day [and don’t know it], I could infect tons of people. “

A positive test result will tell you to cancel your plans and stay home and isolate yourself.

But the negative results don’t mean it’s time to rip the mask off in social circles. Rapid tests can be negative before a party and positive during a party a few hours later, even if you are vaccinated and boosted.

“To say that the negative test means being inside unmasked – I think that needs to be rethought, pronto,” Butler-Wu said.

“Omicron has completely changed the game,” she says. “We know from the Christmas evenings that took place in European locations that these exact scenarios happened: people vaccinated, tests negative and there was still spread.”

Two people are represented.  One is wearing medical scrubs and a face mask as they perform COVID-19, the other is a person who has removed their mask to receive the test in the nose.
A health worker tests a patient for COVID-19 at a test site on 24th and Mission Streets in San Francisco on November 30, 2020. (Beth LaBerge / KQED)

If my test is negative, how accurate is this result?

There can be false negatives, especially soon after exposure when little virus is present in your body, or if the virus is replicating somewhere other than where you were swabbed – for example, in your throat instead of your nose.

However, that doesn’t mean you should use a home test to swab in places other than your nose. A recent viral TikTok video encourages viewers to dab their throats instead, but emergency doctor Marie Mercier says it’s not necessary. She is part of the COVID-19 task force with the San Francisco Department of Public Health.

“You should follow the directions for any home test you have,” she says. “You don’t need to swab your throat in addition to your nose if it’s a nasal test.”

But if your test is negative and you think the result is not correct, it may be a good idea to retest.


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