Have you been tested for COVID-19? The classic test is called PCR (polymerase chain reaction). It detects viral RNA and is considered the gold standard. For this test, you need to go to a testing site, preferably with an appointment. Even then, you may have to wait for a technician to stick a long swab up your nostrils. Then, you should really quarantine until you get the results. Especially during busy times, that can take several days. As a result, a home test for COVID has a timing advantage. While they have been hard to come by, you can now order free tests online.
Government Providing Free Home Test for COVID:
Did you have trouble finding a rapid COVID test over the winter holiday? Lots of people did. Now a government-sponsored website, COVIDtests.gov, has started providing free tests. They won’t ship until late January, but each household can order up to four rapid tests for home use. People who live in zip codes that have been hit especially hard by COVID-19 infections will be given priority.
The administration plans to provide one billion home tests through the program. Those without Internet access will be able to order their tests over the phone.
People who need tests will have to plan ahead, though. The program expects to ship orders between one and two weeks after receiving them. In addition, the post office may take several days for delivery.
What Is the Home Test for COVID?
There was a time when diagnosis was exclusively the doctor’s domain. The idea that patients could have access to tools to help diagnose their own conditions would have been heresy.
That has all changed, and COVID-19 has demonstrated why it is critically important. There are now rapid COVID tests that are available over the counter. You can even buy them online.
Unlike the PCR test that requires a laboratory to perform the analysis, the OTC antigen tests are fast and can be done at home. The antigen tests provide results in 10 to 15 minutes.
New Data on Accuracy:
Readers may have heard about false positive test results, discussed in detail below. As a result, they’d be justified in asking how good the rapid home tests for COVID are.
A Canadian study published in JAMA found that the rate of false positives was very low (JAMA, Feb. 1, 2022). If a person tested positive on the 15-minute antigen test, they were immediately asked to undergo a PCR test that is considered the gold standard. There were over 900,000 rapid antigen tests, with 1,322 positive results. The false positive rate was 0.05% and a number of those resulted from a single bad batch from one manufacturer.
The researchers point out that rapid home tests can identify contagious people with reasonable accuracy. Those individuals should quarantine for at least five days after any symptoms go away. People whose tests are negative can go back to work without much fear of spreading the virus.
Having a Home Test Saved Precious Time:
Q. Thank you for writing about home tests for COVID-19. I developed a headache and sore throat while at work (at a school). Because it took two days to get a PCR test and another three days to get the results, I ended up taking several days off work. Meanwhile, my symptoms quickly abated.
When I was later exposed repeatedly to a student who then tested positive, I opted for the home tests. Since I got negative results on both tests 24 hours apart and had no symptoms, I did not need to take time off. That was well worth the $24!
A. There are now several FDA-approved home tests for COVID-19. While not as accurate as the PCR test, they are much faster and more convenient.
You used your at-home diagnostic kit optimally, taking two tests a day apart. This reduces the chance that the initial negative test was inaccurate.
If more people used such a strategy before interacting with others who might be vulnerable, it could reduce the spread of COVID-19. This would be especially helpful before gathering for family get-togethers over the upcoming holidays.
How Far into Your Nose?
There’s another benefit to a home test for COVID. It doesn’t feel like you are having your sinuses swabbed. You do not have to lean back and have someone “poke” your brain with a very long swab. No one actually does that, even for the PCR, I assure you. It can just feel as if they’re trying to.
The home test uses a shorter swab, and you wield it yourself. Here is the gist of the instructions:
Insert the soft absorbent end of the swab into your nose about 0.4 inch (1 cm). Do not go further than 0.6 inch (1.5 cm). I hate to be crude, but that’s no further than you would go if you were picking your nose.
You then rotate the swab in a circular motion against the wall of your nostril four or five times for about 15 seconds. Repeat the procedure in the other nostril using the same swab. This should not be painful.
Can You Trust a Home Test for COVID?
People want to know if they can trust home tests for COVID-19. As we discussed earlier, false-positive results are rare. These OTC kits are considered “moderate to high” sensitivity when the person being tested has a high level of virus in the nose or throat. With lots of virus in their noses, people are contagious, whether or not they are experiencing any symptoms.
The Difference Between “Sensitivity” and “Specificity”
This gets confusing quite quickly, so please hang on. In the lab biz, experts use the word SENSITIVITY to mean how well the test in question delivers an accurate positive test result.
SPECIFICITY means how well the test identifies a negative result.
Think of it as an umpire behind the plate at the World Series. The ump calls both strikes and balls. In other words, did the pitch go into the strike zone or did the pitch miss the strike zone? With electronic monitoring, we can now verify each pitch to determine whether the umpire called the pitch correctly.
Let’s designate correctly called strikes sensitivity. A good umpire may correctly call strikes 90% of the time, verified by the computerized camera. In other words, the pitcher threw a strike and the umpire called a strike accurately 90% of the time.
In the case of COVID, the patient was infected with SARS-CoV-2 and the test accurately identified the patient as positive with the same accuracy as the umpire: a sensitivity of 90%.
If the sensitivity of the test were low, say only accurate about 40% of the time, it would miss a lot of sick people. 60% of the time they would be identified as healthy but go on about their lives spreading the virus to friends, family and complete strangers.
What about Specificity?
In this mangled analogy, I am calling specificity correctly called balls. In other words, the umpire correctly identified the ball as outside the strike zone. An umpire may be terrific at correctly calling strikes but mess up when it comes to pitches that are outside the strike zone.
Let’s say the umpire calls the “balls” correct 75% of the time. In other words, a “bad” pitch that is out of the strike zone gets called a strike by mistake 25% of the time by our crappy umpire. A low-specificity test, as in our COVID example, could say the patient is positive for SARS-CoV-2 when in fact he is perfectly healthy.
In an ideal world, umpires would almost always call both balls and strikes perfectly and a COVID test would accurately identify people who have the virus and not mistakenly flag healthy people as infected.
How Good is PCR?
The College of American Pathologists states that the sensitivity of the PCR test is about 80% and the specificity is about 98-99%. Consequently, the PCR test almost never says you’re sick when really you’re not. Sometimes, though, it misses people who have COVID but the test says they are perfectly healthy.
Some At-Home Antigen Tests:
You can now purchase a home test for COVID at an affordable price, anywhere from about $15 to $40. According to ConsumerLab.com, both Quidel QuickVue and FlowFlex do a good job of detecting the Omicron variant.
“The Ellume COVID-19 Home Test correctly identified 96% of positive samples and 100% of negative samples in individuals with symptoms. In people without symptoms, the test correctly identified 91% of positive samples and 96% of negative samples. The Ellume COVID-19 Home Test uses an analyzer that connects with a software application on a smartphone to help users perform the test and interpret results. Results are delivered in as little as 20 minutes to individuals via their smartphone.”
The BinaxNOW COVID-19 Antigen Self Test comes with the following information:
“If you have a positive test result, it is very likely that you have COVID-19 because proteins from the virus that causes COVID-19 were found in your sample. Therefore, it is also likely that you may be placed in isolation to avoid spreading the virus to others. There is a very small chance that this test can give a positive result that is wrong (a false positive result).”
If used within seven days of the first symptoms, sensitivity is about 85% and specificity is about 99%. What does that mean? This test is identifying about 85% of the people who have COVID-19. It is missing as many as 15%. That is to say, some people get a negative test result but they actually have the coronavirus.
On the other hand, if the test says you are negative, the chances are pretty good that you do not have the virus.
The fact sheet that comes with the QuickVue At-Home COVID-19 Test states that it:
“can be used by individuals with or without symptoms or other epidemiological reasons to suspect COVID-19 when tested twice over two or three days with at least 24 hours and no more than 36 hours between tests.”
This OTC test was announced by the FDA on October 4, 2021. It is the Flowflex COVID-19 Home Test.
The FDA offered this addendum to its emergency use authorization message:
“This action highlights our continued commitment to increasing the availability of appropriately accurate and reliable OTC tests to meet public health needs and increase access to testing for consumers.”
“Today’s authorization for the ACON Laboratories Flowflex COVID-19 Home Test should significantly increase the availability of rapid, at-home tests and is expected to double rapid at-home testing capacity in the U.S. over the next several weeks. By years end, the manufacturer plans to produce more than 100 million tests per month, and this number will rise to 200 million per month by February 2022.”
Other At-Home Tests include:
- CareStart COVID-19 Antigen Test
- InteliSwab COVID-19 Rapid Test
The Bottom Line on Accuracy:
A home test for COVID will never be 100% accurate. That’s partly because timing is everything.
If you catch the virus but do not yet have any symptoms and very little virus in your nasal passages, the test may come back falsely negative. We see such tests as helpful, but not foolproof.
Some Scenarios for a Home Test for COVID:
The Football Game:
We received a question from someone who wanted to know what to do about an upcoming social event. He told us that he developed a cough last Friday and woke up Saturday with a sore throat. Otherwise, he felt fine.
He was planning to watch a football game with his friends on Sunday and wondered if a home test for COVID could determine if he were contagious. We advised him to do the test. It came back negative!
He tested himself again before leaving for his friend’s house. Still negative! He enjoyed the game. His cough disappeared and the sore throat was gone by Monday. Without the test he might have stayed home.
Vaccinated but Exposed:
Another scenario might involve someone who is fully vaccinated but is contacted by a co-worker who reports coming down with COVID. Before rushing off to get a PCR test, such a person could start with a home test for COVID and monitor progress over the next several days.
Preparing for the Holidays:
It won’t be long before we start thinking about visiting friends and family for the holidays. People who will be flying will be making airplane reservations.
No one wants to spread the virus to loved ones. To prevent such an event, test yourself a few days before departure and then again the evening before you leave. A negative test may not be foolproof, but it is way better than nothing!
When you return from family gatherings you will want to test again if you develop any symptoms of COVID. Be vigilant for fever, shortness of breath, sore throat, runny nose, congestion, loss of taste or smell, headache, diarrhea, body aches or vomiting. Any such symptoms should trigger a test! If it comes up positive, quarantine! You do not want to spread COVID-19 to anyone else.
The FDA and Home Tests:
We are pleased to see that the FDA has moved so promptly to approve over-the-counter home tests for COVID-19. We were intrigued to see that the makers of the Ellume COVID-19 Home Test have announced that they will also bring out a home test for influenza in the future.
“Test results are displayed on the user’s phone within 12 minutes of completing the test.”
A home test for COVID and flu will help people quarantine if they are positive. That will reduce the spread of these viral infections.
There are antiviral drugs against influenza. As a result, a rapid diagnosis could allow a physician to prescribe a medication such as oseltamivir (Tamiflu) or baloxavir (Xofluza) to speed recovery.
Any oral drug for COVID-19, such as Paxlovid or molnupiravir, works best when taken early in the infection. A home test for COVID could help make that possible!
What Do You Think?
Have you been tested for COVID-19? What was that like? Have you tried a home test for COVID? What did you discover? How did that affect your behavior?
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