Since the coronavirus pandemic’s earliest days, public health experts have agreed that intercepting and minimizing outbreaks would hinge on our ability to answer a seemingly simple question: Do I have the virus?
Compared to this time last year, consumers have far more COVID-19 testing options available to them—including, now, a handful of new tests that can be administered from the comfort of home.
“Each type of test has its place,” says Patrick Godbey, lab director of Southeast Georgia Regional Health System and Southeastern Pathology Associates. “You use the different types of tests for different situations.” And the advent of do-it-yourself tests, he says, “has the potential to be tremendous.”
Most of the at-home tests authorized by the US Food and Drug Administration to date are kits that ask users to collect their own spit or swab samples and mail them to a lab for processing. But in recent months, the FDA has also granted emergency use to at least six at-home tests that return results on the spot, within an hour.
Experts hope the broadening selection of testing options will help prevent people with asymptomatic infections from turning into unwitting super-spreaders.
“The three most dangerous words during COVID are ‘I feel fine,’” says Mara Aspinall, co-founder of the biomedical diagnostics program at Arizona State University. “We need to be testing regularly. No test is perfect, and this disease is, unfortunately, sneaky.”
How do at-home rapid COVID-19 tests stack up?
So far, the US has administered more than 355 million COVID-19 diagnostic tests, according to the Centers for Disease Control and Prevention. Many of these tests use a molecular technique called polymerase chain reaction, or PCR, that looks for small pieces of the virus’s genetic material in a sample (usually a swab of the nose or upper throat, but sometimes saliva) taken by a health worker at a testing site.
Because PCR is a lab test, it can take a few hours or days to turn around results. But the technique is highly accurate at picking up positive cases since it can confirm the virus’s genetic presence—even if faint—in a given sample. “It is considered the gold standard,” says Thomas Denny, a professor of medicine at Duke University Medical Center.
Most of the newly-approved at-home kits that return results right away use a different, much faster technique. Instead of looking for traces of the virus’s genetic footprint, these tests—called antigen tests—screen for fragments of proteins shed by the virus.
Antigen tests are good at quickly identifying people with larger amounts of the virus, and therefore, proteins shed by it. These individuals are typically more infectious and should self-quarantine.
However, antigen tests are far less sensitive than PCR tests and are more likely to lead to false negatives—in which the test gives a negative result even though the person has COVID-19—especially in folks who are asymptomatic. Depending on the stage of an infection, it is possible for someone to be negative according to an antigen test but positive with PCR, or vice versa, experts warn.
Experts also stress the danger of mishandling at-home tests, since (after all) most of us are not professionally trained to collect saliva, take nasal swabs, or properly store sensitive testing materials.
“You have people who are not used to performing laboratory tests performing those tests,” says Godbey, who also serves as president of the College of American Pathologists. “They need to be meticulous about every aspect.”
And regardless of what type of test you’re taking, there’s always the possibility of picking up the virus right afterward—which makes it nearly impossible to ever definitely conclude someone is not infected.
“Testing is only a snapshot of a particular time,” Denny says, “whether you do it at home or at a testing center.”
How easy are at-home tests to use?
Popular Science staff ordered and tested a few of these at-home tests to evaluate their ease-of-use, identify any struggle points, and determine how useful these are for consumers overall.
DIY Assistant Editor Sandra Gutierrez tried out an antigen test made by Australian manufacturer Ellume, which was the first rapid, fully at-home antigen COVID-19 test authorized by the FDA. The test costs about $30 online and at pharmacies, and delivers results within 15 minutes.
The self-administered nasal swab is just as annoying as when it’s taken by a professional, according to Gutierrez. “If you think that controlling the swab makes it any better,” she says, “it does not.” But overall, Ellume’s testing process was fairly easy.
Since that test was authorized back in December, even more at-home tests have been authorized for use by the federal government.
Abbott’s BinaxNOW Self-test
Another at-home antigen test, Abbott’s BinaxNOW, promises results within 15 minutes and is available now at major drugstore chains including Walgreens and CVS at $24 per box. Each box comes with two tests; both should be used by the same individual, with the second taken 36 hours after the first. This can help compensate for the typical downside of an antigen test—taking two makes it less likely to miss an infection just because it’s new, especially if you isolate at home in the interim.
For those who are willing to quarantine for a few days while waiting for COVID test results, mail-in kits might be a better option. These kits still rely on the user to collect the sample, but the analysis is done in the lab, using the same technique that PCR tests done at a doctor’s office or clinic employ. These tend to be a little more expensive, but they’re also more accurate.
As Science Editor Claire Maldarelli learned, one of these at-home collection kits, from DxTerity, will cost you $110, doesn’t require a prescription (some kits do), and you can order it on Amazon. The COVID test requires a saliva sample, rather than a nasal swab. It was, however, “extremely easy to use,” she says, with easy-to-follow instructions and clearly-labeled equipment. Her only additional note: “You need a lot more saliva than you realize!”
Labcorp Pixel and Quest Diagnostics
Another mail-in alternative is Labcorp’s Pixel at-home kit, which runs $119 out of pocket and can be ordered on the company’s website without a prescription. Quest Diagnostics makes a similar at-home kit, priced at about $138, which also gets sent back to the lab for testing.
Associate technology editor Rob Verger tried Labcorp’s Pixel kit out, and found its 12-step process fairly painless. He did note that the process requires setting up an account with the company and dropping the test off at a FedEx location in time for a same-day express service—“so you’ll need to fit that step and timing into your plans.”
His verdict: “As easy as a home COVID test could be, it seems, but you still need to devote a little bit of time to doing it carefully.”
Other at-home COVID-19 tests to consider
Beyond the handful of options tested by Popular Science, a small cadre of new tests offer actual molecular analysis (like PCR testing) from home.
Cue’s at-home testing cartridge looks for the coronavirus’s genetic material, like a lab test, but returns results in about 20 minutes. Its price is not yet available, and while it has been granted emergency-use authorization from the FDA, the test is not yet available to the public, though the company says it hopes its tests will be ready for consumers “soon.” Lucira’s $55 at-home COVID-19 test also uses a molecular approach and returns results within 30 minutes.
There could be even more tech alternatives coming down the line. Scientists at The Ohio State University have developed a cheap, reusable breathalyzer-like device to detect coronavirus infections (it has been submitted to the FDA but has not yet received emergency use authorization, according to OSU’s campus newspaper, The Lantern).
How accurate are the at-home COVID-19 tests?
The accuracy of COVID-19 tests are based on two main factors: Sensitivity and specificity. A test’s sensitivity is how well it can correctly identify a person who has the disease, in this case, COVID-19; a test’s specificity measures how well it identifies those without the disease. The closer each of those are to 100 percent, the more accurate the test.
In general, PCR tests are more sensitive and specific than rapid antigen tests. Because Quest’s and Labcorp’s tests are taken at home and sent back to their labs for testing, each of those tests’ sensitivities and specificities are close to 100 percent. DxTerity’s test, which uses a saliva sample that’s sent to the company’s lab for testing, has a 97.2 percent sensitivity and a 92.5 percent specificity.
Ellume, maker of one of the handful of tests in which the samples and results are given at home, reported that its test identifies positive cases (sensitivity) 95 percent of the time and negative cases (specificity) 97 percent of the time. This was based on a study of 198 symptomatic and asymptomatic users and the results were compared against PCR testing.
Abbott pitted its BinaxNOW Self Test—another totally at-home COVID-19 test—against PCR tests in 460 symptomatic patients. The company found that if users were within seven days of symptom onset, BinaxNOW agreed with positive PCR results about 85 percent of the time and with negative PCR results about 98 percent of the time.
But when zoomed out to users within two weeks of symptoms, agreement with positive PCR results fell to 77 percent. Independent tests of BinaxNOW suggest the antigen test correctly identifies the virus 64 percent of the time for those with symptoms, and only 35 percent of the time in asymptomatic people. However, it did accurately identify negative results (in those that don’t have COVID-19 according to PCR) almost 100 percent of the time.
The last test we looked at, Cue, which is not yet available to the public, was evaluated in 292 symptomatic and asymptomatic individuals by a team of researchers at the Mayo Clinic, who recently published their results in the journal Diagnostic Microbiology and Infectious Disease. The Mayo Clinic team found that the Cue test had a positivity rate of between 91.7 and 95.7 percent and a specificity of 98.4 percent.
When to use an at-home COVID-19 test
Experts say that diagnostic testing—whether at home or at clinics and community sites—will continue to be critical during the pandemic’s last stretch.
Right now, there’s a lot to be hopeful about: The COVID-19 death toll has dropped precipitously since its winter peak and more than one in three US adults are fully vaccinated. But there are still about 55,000 new cases daily, and about 660 lives are lost each day to the disease.
“Now’s not the time to give up on testing,” Denny says. “We need to double down.”
Overall, experts say, an expanded array of options for identifying positive cases will help us curb their proliferation. “The more we can do simple, regular, at-home testing, the less we need it,” Aspinall says. “It’ll become a habit, as easy as brushing your teeth.”
In the coming months, home tests can prevent infected people from spreading the coronavirus while sitting in a doctor’s office. They can also fill in gaps for those who may have less access to in-person testing.
And they could be deployed during local outbreaks or clusters at nursing homes, prisons, or other residential facilities to quickly determine who’s sick, says Prathit Kulkarni, an infectious disease specialist at Baylor College of Medicine.
So how should you approach at-home tests? If you’re unvaccinated and symptomatic, they’re a great way to confirm a COVID-19 infection without risking a trip out of the house.
If you’re unvaccinated and have no symptoms, and just want to know whether you can safely attend a family dinner or soccer game, an at-home test remains an imperfect way of self-screening. Remember: If the test comes back negative, there’s still the chance the result is false and you could accidentally expose others by being within six feet of them without a mask on.
In recent weeks, the FDA has authorized so-called “serial” antigen tests that can be taken within days of each other, increasing confidence in the test results. That’s the case for Abbott’s BinaxNOW self-screen, which comes in a pack of two tests to be taken 36 hours apart.
Otherwise, there is an even better way to prevent yourself from spreading COVID-19 at gatherings, Kulkarni says: Get vaccinated. Being fully vaccinated significantly reduces your risk of getting and spreading COVID-19.