• The San Juan Daily Star

At-home COVID tests add a layer of precaution


By Tara Parker-Pope


For many people, the hardest part of pandemic life after vaccination is the uncertainty about risk. But rapid home testing can lower risk, ease the worry and help you get back to life.


Testing is not a substitute for getting the vaccine. But as long as large numbers of people remain unvaccinated and continue to spread the coronavirus, vaccinated people are at risk for so-called breakthrough infections, which often come with mild symptoms or none at all.


For the vaccinated, a negative test is like a one-day anxiety-free pass. At-home rapid tests can tell people within minutes whether they are contagious with COVID-19. If you have been traveling through airports or you have recently spent time at a crowded outdoor concert, a few rapid tests, taken days apart, can show that you are unlikely to be spreading the coronavirus after attending those higher-risk events.


One big problem is that the tests can be hard to find, but that should improve soon with the authorization of a new test and an investment of $1 billion in home testing from the Biden administration. Some stores do still have tests in stock, but it may require some effort to find them. If you find a stash of tests, do not hoard. Tens of millions more tests are expected to arrive on the market in the coming weeks, and by December, 200 million rapid tests will be available to Americans each month.


No test is a 100% guarantee, but given that your vaccine already protects you, a home test is another layer of precaution to lower risk. Unvaccinated people can benefit from using home tests as well, but they should not rely on testing as a substitute for a vaccine. Home tests are particularly useful for families with young children who are not yet eligible for vaccination and for anyone with an at-risk family member.


“Testing is an information business, and that information is liberating,” said Mara Aspinall, an expert in biomedical diagnostics at Arizona State University who is also on the board of OraSure, which makes rapid COVID-19 tests.


In the United States, the tests can range from $7 to $12 each, making them too expensive for most people to use frequently. But with cold weather approaching and winter holidays ahead, home tests still can be a helpful way to lower the risk of indoor gatherings.


How do they work?


The rapid home tests work much like a pregnancy test, with a pink line indicating you are positive for the coronavirus. The tests all require you to swizzle a swab in both nostrils. Depending on the test, you may insert the swab into a special card reader or dip the swab in a solution and use a test strip, then wait 10-15 minutes for the result.


The rapid home antigen tests available in the United States include Abbott’s BinaxNOW, Quidel’s QuickVue, Australia’s Ellume and the recently authorized test by Acon Labs, Flowflex. The tests typically are packaged two per box.


A rapid home molecular test, Lucira, uses a different technology and is similar to the test you might get at the doctor’s office. But it is hard to find, and at a cost of about $50, it is not a practical option for most people.


Are home tests reliable?


Although no test is 100% accurate, the new rapid home tests are highly reliable for telling you whether you are contagious on a given day. Rapid tests identify about 98% of cases in which a person is infectious.


But it is also possible to test negative on one day and then test positive a few days later. That does not mean the first test was wrong; it just means on the day you tested, you were not infectious yet.


“If the test is negative and you later test positive, it’s not wrong,” said Gigi Gronvall, an associate professor at the Johns Hopkins Bloomberg School of Public Health. “The question the rapid antigen test is asking is, do you have a lot of virus in your nose at this moment: yes or no?”


So how should I use the tests?


Most home tests advise testing twice over a three-day period, with at least 36 hours between tests. The timing of the test matters. Using one test is a useful precaution right before seeing friends or family members who want to gather indoors and unmasked. A quick test can also help a parent make sure a child’s cough or sniffle is not COVID-19.


If you are worried that you have been exposed to COVID-19, you should take two tests over a three- to four-day period. The Centers for Disease Control and Prevention says the best testing window after a potential exposure is three to five days after the high-risk event or contact with an infected person.


The bottom line is that the more often you use the tests, the better, said Dr. Michael Mina, a public health researcher at Harvard and a proponent of rapid testing. (Mina advises Detect Inc., a diagnostics company working on a rapid molecular test.) If you want to spend time with a medically vulnerable person, you should take a test a few days before seeing them and then take another test on the day of the visit.


What do I do if the test is positive?


Most of the time, a positive result means you have the coronavirus, particularly if you have symptoms. But false positives do happen. If there is reason to doubt a positive result, take another test, preferably from a different manufacturer or at a testing center. People hosting large events, such as weddings, and using the tests to screen guests should have a few extra tests on hand from a different brand for those guests who test positive. You can be confident in the result if the second test is negative, Mina said.


“It would be really rare for someone to have a true positive and then have a second test show a false negative result,” he said.


How do I find a home test?


Although supplies are expected to improve in the coming weeks, the tests can be difficult to find right now. Try the websites of stores such as CVS, Walgreens, Costco or Walmart, or check with a local drugstore. I recently searched the CVS website for a friend in New Jersey and found BinaxNOW tests at a store about 30 minutes away. When my friend arrived, he found the shelves stacked with tests.


A word of warning: Make sure you search by brand name. If a store is sold out of a rapid test, the website may direct you to a different type of test, called a home collection test, that requires you to mail the sample to get the result. But hold out until you find a rapid test. “The fact that they are rapid,” said Gronvall, of Johns Hopkins, is what “makes them a really great test to make sure somebody is not infectious at that moment.”