How at-home COVID tests can make holiday gatherings safer

Though nearly 63% of Californians are fully vaccinated, some public health officials worry that large gatherings this holiday season could lead to large outbreaks of COVID-19. But families looking to reunite have at least one means of preventing infection they didn’t have last year: rapid at-home test kits.

The kits aren’t foolproof, and most aren’t as reliable as the lab-based alternative when it comes to detecting coronavirus infections in their earliest stages. Also, if you have a house full of people to test, the cost can be high.

For the record:

2:57 p.m. Nov. 22, 2021An earlier version of this story incorrectly reported that the CDC recommended that unvaccinated travelers quarantine for seven days upon arrival at destination. The CDC recommends that unvaccinated travelers self-quarantine for seven to 10 days after returning from their trip.

However, in the right circumstances, a home test can alert you in minutes if Cousin Antoine’s cough or Aunt Maggie’s muscle aches are signs of a potentially serious threat to the rest of the family. Even better, the tests can make it easier for your invited guests to check for an active infection before they roll into your home.

Another key caveat: If you haven’t been fully vaccinated, the Centers for Disease Control and Prevention is warning against traveling to this holiday meeting. And if you’re determined to travel unvaccinated, the CDC recommends doing so only if you test negative for coronavirus one to three days before departure and are quarantined for seven to 10 days upon your return.

Here’s an overview of how the tests work, how reliable the results are, who runs them, where to find them, and how much they cost.

What are rapid at-home COVID tests?

The keyword here is “fast” as results are returned in about 15 minutes. Unlike the self-test kits that require you to send to a lab for processing, the rapid kits allow you to process your samples at home — in fact, most of them allow you to watch the results slowly emerge on a test strip, just like you would maybe look at a picture on a Polaroid (but with higher stakes).

The U.S. Food and Drug Administration has approved two types of emergency rapid tests: molecular and antigen tests. The molecular tests, which have a higher sensitivity but are associated with higher costs, examine the genome of your sample for the presence of the SARS-CoV-2 virus. The antigen tests look for a protein that binds to the RNA of the coronavirus.

Only two of the three approved at-home molecular tests — the Lucira CHECK-IT kit and the Cue Health kit — are now available online, and they’re expensive: Amazon sells Luciras for $89 a test, and Cue sells a pack with three of them trials for $225 plus $249 for the base unit (it also offers a membership-based plan). A third company, Detect, says its molecular test will be available this month for less than $50 per test on the company’s website, not including the cost of the reusable base unit, which sells for less than $40.

A quick search for antigen tests, however, turned up six of the nine approved tests available to US consumers in stores or online from one of two different manufacturers:

Another Celltrion antigen test is available in bulk from online medical supply stores for around $10 per test.

Different antigen test kits have different features – for example, some have smartphone apps that can show your test result, which would be useful if you’re asked to prove a negative test. And the performance of the tests can vary, although all were good enough to receive FDA emergency use approval.

dr Ashish K. Jha, dean of Brown University School of Public Health, said the BinaxNow test is the most widely used and therefore has a greater track record than the other tests. But he said people shouldn’t pay too much attention to brand names because testing was relatively close. “Any of the tests you can find is a lot better than not having any tests,” he said.

How reliable are the results?

The coronavirus that causes COVID-19 disease can take several days to build up steam (or “viral load”), meaning you’re unlikely to show symptoms or be contagious to others immediately after contracting it. For this reason, health officials advise you not to get tested immediately after exposure to anyone who may be contagious.

However, molecular tests use chemical techniques to amplify the amount of genetic material in a sample, allowing them to detect the presence of the coronavirus at a very early stage — in some cases even before a person can pass the infection on to others. On the other hand, they can also find leftover traces of the virus after a person is no longer contagious. And like any test, they are subject to contamination and other interference that can lead to erroneous results, including the occasional false positive. It’s not common, but it’s more likely to occur in communities where cases of the disease are few.

Antigenic testing has proven to be as effective as molecular testing in preventing false positive results. And according to the CDC, these tests are also just as good at detecting COVID in someone showing symptoms of the disease, such as a cough, fever and sore throat.

Where testing falls short, the CDC warns, are people who have the virus but are not showing symptoms, particularly if they are in the early stages of infection and may not yet have enough viral load to infect others. The agency recommends doing a second antigen test a few days after the first, which is why the kits are sold in packs of two.

If you have not been vaccinated and have been in close contact with someone who has had COVID at any time in the past two weeks, the CDC recommends that you have molecular testing just to make sure you are not infected.

What is the best use of rapid tests?

Testing can reduce risk in a variety of vacation scenarios, but Jha and Dr. Robert Wachter, chair of the medical school at UC San Francisco School of Medicine, said it makes the most sense in two situations: when unvaccinated people join you for the holidays, or whether people in your party would be at high risk of fatal complications if they would contract a breakthrough case of COVID-19. “Besides, while it might make a gathering a little bit safer, I don’t think it’s worth spending a few hundred dollars to test about 10 people,” Wachter said in an email.

Another factor in favor of testing is the high rate of coronavirus infection in the community, Jha said. But which community determines the level of risk? This can be difficult to figure out when you have guests from different parts of the country.

When and how often you should take a test depends on the type of meeting. “Rapid testing is a measure of contagiousness,” Jha said, “and so you want to test as closely as possible to how you’re socializing with people.” If it’s just a Thanksgiving meal, Jha said, “The ideal situation would be to test on Thursday morning.”

But if it’s a holiday weekend visit, he and Wachter suggested testing more than once — say just before arrival and again in a day or two — especially if you’re in the presence of unvaccinated people. “Two negative tests, you’re really good to go,” Jha said, adding that you could even take a test daily if you’re around people who are at high risk of COVID-19 complications .

“In an unvaccinated population, a single test probably isn’t good enough,” Jha said. As evidence, he pointed to the ceremony President Trump held last year for new Supreme Court Justice Amy Coney Barrett. Participants had to have a negative test result to be admitted, but it still became something close to a superspreader event.

how do you test yourself

The typical process begins with taking a sterile swab from the kit and tracing the inside of each nostril several times. That collects the sample. The next step depends on the type of test.

In molecular testing, the swab is inserted into a small container where the sample is mixed with a reagent, a substance that begins the process of revealing the sample’s genetic make-up. The container is then placed in a base unit where the magic (technically the Isothermal Reinforcement) happens. The results appear on the base unit or in a smartphone app.

For antigen testing, the swab is placed in a disposable reader (often paper) where it meets a test strip. You add a few drops of the kit’s reagent and then observe if the strip shows a positive, negative, or inconclusive result.

Be sure to read and follow the instructions carefully to collect a proper sample and avoid contamination. For example, the popular BinaxNow test has you swab each of your nostrils for 15 seconds and rotate the swab three times after placing it in the reagent. How at-home COVID tests can make holiday gatherings safer

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