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How Accurate Is Your At-Home Covid-19 Test?

If your favorite group chat blew up when the US government announced it was finally dropping promised 500 million at-home Covid-19 rapid tests, you’re not alone. As Omicron continues to spread, the USPS is starting to dole them out to households around the country. (If you haven’t ordered a set yet, you can here.)

If you’re vaccinated, you’re much less likely to be hospitalized with a case of Covid-19, but breakthrough cases have become more and more common. In the midst of the recent spread, at-home rapid antigen tests have been flying off shelves.  

Dr. Anthony Fauci cautiously says he thinks the United States’ current wave of Covid-19 is “going in the right direction,” but warns of a few hard weeks before we get there. (As of January 21, the US was still experiencing an average of around 20,000 Covid-19 hospitalizations per day; NBC has reported that 1 in 5 hospitals with ICUs don’t have any beds left in their critical care units.)

So for now, the reality is you’ll probably want some tests on hand.

There are a few different types of tests to be aware of. The FDA has approved a slew of rapid-antigen tests. You’ll find these, most of which come with a swab and return results in around 15 minutes, at the store or at Covid-19 testing sites. PCR tests, which you can get at a Covid-19 testing site, produce more accurate results in as little as 24 hours.

All this renewed interest in testing has brought up a lot of new questions. We checked in with epidemiologist Thomas Duszynski to clear up any confusion over what type of test you should seek out, the accuracy of at-home testing, how to make sure you’re doing it correctly and more. 

First of all, how accurate are the at-home rapid Covid-19 antigen tests?

At a minimum, they’re usually around 80 percent accurate at detecting Covid-19, which is pretty good for a rapid at-home test.

Say you develop symptoms. Should you take an at-home rapid test or rush to get a PCR test? How do the two types of tests compare?

Rapid tests are what we consider screening tests. There’s a high likelihood that the test is accurate. If the test says you have the disease, the likelihood of you having the disease is pretty high. Then you can go back and confirm with a PCR test if you wish.

However, the disease process is going to be a little bit different for everyone. It gets a little complicated when you explain this, but during the early onset of symptoms, you may not have enough virus in your system to be detected by a rapid at-home antigen test just yet. The first couple of hours of having symptoms may not produce enough virus to detect it. Twenty-four hours later, you take a test again, your body is under attack from the virus and the viral replication is really high at that point, so then there is a better chance to capture it in a rapid at-home antigen test.

The PCR test is the gold standard we rely on. They are more sensitive because they capture and amplify what’s there. It can detect Covid-19 with less virus present. Because PCRs are more intensive, they also allow public health officials to do more sequencing. They can use data from PCRs identify whether a case is the Delta variant, Omicron or something else. With a rapid test, they don’t have those capabilities. 

Say you did one at-home test and it’s negative, but you still have bad symptoms. How many at-home tests do you recommend people take to confirm a positive?

I would just take one at this point. You have to remember that there are other things out there right now, including influenza, that can look like Covid-19. If it is negative, contact your PCP and say, “I’ve taken this at-home test, it’s negative, I have these signs and symptoms.” They can give you some advice on whether or not to take another at-home test. 

How good do you have to be at doing an at-home rapid antigen test to get an accurate result?

I did a rapid at-home test Saturday. Here are a couple of really important points:

  • Read the directions completely before you do anything else. Make sure you understand what they are telling you to do. Many of the directions come with little pictures of what to do and when. These are very helpful. Just understanding the process from beginning to end can help eliminate any mistakes or errors that can compromise the results.
  • Wash your hands before you do the test, so you don’t contaminate any of its pieces. 
  • Wipe down any surfaces before you start taking the test. If you’re setting up your test at the kitchen table, let’s clean the kitchen table first. It sounds silly, but it can make a difference. 
  • Time it. If it says to wait 15 minutes, wait 15 minutes. 

The government is sending out all these tests and you can’t choose which brand you’re getting. Does that matter?

The ones that you’re going to get from the federal government, the USPS, the brand won’t make a difference. The accuracy is going to be similar. And again, remember, these are screening tests. 

Does it matter how quickly the sample turns (or doesn’t turn) red?

On average, the test will produce results in 15 minutes. If it turns red in 11 minutes, it doesn’t make a difference. 

There are also saliva Covid-19 tests. Compared to the nose swab, is there any difference between the two?

There really isn’t. They’re just taking different samples. Some people don’t like having anything put up their nose. It can be a little uncomfortable.

How soon after exposure should you take a Covid-19 test?

The challenge here is everyone is going to be a little different. Who were you exposed to? How long were you exposed? Did you wear masks? There’s a lot of variables that go into calculating that. The CDC currently recommends getting tested five days after exposure, that is, if you don’t develop symptoms. 

How are public health officials keeping track of cases when so many people are taking at-home Covid-19 tests and aren’t necessarily reporting them?

This is a thing we’ve been talking about because it’s been quite a challenge. The at-home cases don’t always get collected or reported. When you’re looking at the stats on the public health website, that’s a percentage of the population that got tested at a testing facility and then those test results were reported officials (confidentially, of course).

But the at-home tests, there is no requirement to call a certain number if you test positive. We’re asking people to contact their physician’s office if they do test positive to see if they should follow up with a PCR to get advice on how to take care of themselves.

Then if they can record it, wonderful. That at least gives us a better idea of how much disease is in the community at a time. The at-home cases don’t always get collected or reported. 

After recovering from Covid-19, some people have reported testing positive on PCR tests for weeks after. Why is that and should people be worried if they’re still testing positive weeks later?

To be honest, that can be very common. PCR tests can take just a little bit of virus and amplify it so that we can see it. So even though we may be finding finding a little virus in your nose, or in the back of your throat, you’re likely less infectious.

The ability to spread disease goes down rapidly as the amount of virus decreases.

But if it’s still in your system for weeks after you have symptoms, how might that impact you?

Well, that’s the danger. This is why we’ve been telling people to get vaccinated and try not to get infected. We know what’s in the vaccine. Billions of people have been vaccinated with very little reactions, other than developing immunity.

We still don’t know the long-term effects of being infected. We know this virus can attack just about any organ in the body, and we don’t know what kind of damage it will do over the long run. Ten years from now, will there be more heart damage in people who have been infected versus than those who haven’t been? We don’t know those answers yet. And that’s why it’s so important to be protected. 

This interview has been edited and condensed. 

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Show Comments (1)
  1. Alexis

    I don’t think these test work I got the free ones they sent out I got sick Fri night I took the instant test Sunday and it was negative for both my husband and I he has really bad symptoms but they were negative my job requires an actual test before going back so I went yesterday (Tuesday) and it came back positive.

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