Home COVID-19 Antigen Test: What You Should Know

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For the low-risk COVID-19 test, the rapid antigen test provides a quick and easy way to screen for SARS-CoV-2 at home. They are especially useful if you know or suspect that you have been exposed to the coronavirus but cannot get a professional test (or wait for the results).
The FDA-authorized home antigen diagnostic test can detect active COVID-19 infection, including asymptomatic individuals, in about 15 minutes. Overall, these tests are not as sensitive as molecular diagnostic tests performed in laboratories. Nonetheless, the results of a home antigen test can provide additional data—if not completely relieved—about a person’s COVID-19 status, especially if you test regularly. Depending on your situation, it may make sense to have some of these tests on hand.
Remember, a negative result does not necessarily mean that someone does not have COVID-19, and these tests are not meant to be used as the only diagnostic method. Dr. Matthew McCarthy, associate professor of medicine at Weill Cornell School of Medicine, said: “Antigen testing is a cheap and simple way to identify people who may be infectious.” For people without a known history of COVID-19 exposure, “if You are going to Thanksgiving, where there are 20 people and they are all vaccinated, you can do an antigen test before you go to make sure you did not bring the virus into the party,” he said, citing a potential use.
It may also be appropriate to conduct a rapid antigen test before interacting with people who may be more susceptible to the virus. Dr. Claire Rock, a clinical epidemiologist at the Johns Hopkins University School of Medicine, said: “Even fully vaccinated people may want to take one of these convenient home tests before spending time with grandma,” who runs COVID-19 infection control consulting company.
COVID-19 antigen testing at home can be convenient and fast. There is no need to wait for an appointment (or order a kit by mail and ship samples) and then wait for the results of a molecular diagnostic test. By performing an antigen test at home, you can usually take 15 minutes from the swab to the result. These tests are usually easy to perform, and you can read the results manually (such as using a home pregnancy test) or digitally (using an app).
The COVID-19 antigen test is not as sensitive as molecular diagnostics. Unlike the molecular diagnostic test of COVID-19, which involves amplifying the viral nucleic acid to a level that is easier to detect, the antigen test can detect traces of the unamplified virus, so it is not easy to detect small signals. (Do not confuse the antigen test with the antibody test. The antibody test is designed to detect antibodies that react to the virus and is not used for diagnostic purposes.)
Although home antigen testing is not foolproof, when detecting active COVID-19 cases, even molecular diagnostic methods like gold standard PCR testing are not always accurate, because the results depend on, among other things, the timing of the test. . If you wiped it prematurely after contact, your test result may be negative even if you have the virus. After you are no longer infectious, you can also receive a positive PCR test result.
Clinical epidemiologist Rock said that compared with the molecular diagnosis of COVID-19, antigen tests are “not so sensitive if we want to know if there are any tiny viruses, but if we are looking for them, they are very sensitive” see To see if there is a certain degree of virus, we must worry that someone will infect others. ”

“We usually recommend testing three to five days after exposure.”-Dr. Matthew McCarthy, Weill Cornell School of Medicine
The accuracy of the home antigen test depends in part on the sensitivity of the test (the ability of the test report to detect true positives), the specificity of the test (the ability of the report to detect true negatives), and sample integrity (whether the swab contains enough samples or swabs The solution is contaminated with another pathogen), regardless of whether the manufacturer’s instructions have been fully followed, the time since the last known or suspected contact and/or the onset of symptoms, and the viral load at the time of the test. (These tests are currently authorized for people as young as 2 years old, provided that any samples of children are obtained and processed by adults.)
For tests considered for emergency use authorization, the test manufacturer must submit clinical data to the FDA to demonstrate the sensitivity and specificity of the test. Some independent studies have shown that the sensitivity and specificity of certain antigen tests are much lower, especially when they are used in asymptomatic individuals. (There is currently a commercially available SARS-CoV-2 molecular diagnostic test that has been authorized by the FDA and can be used at home for emergency use, which means you don’t need to send samples to the laboratory for testing: Lucira COVID-19 All- In-One Test Kit. Compared with some FDA-authorized home antigen tests, it has a slightly higher sensitivity (95.2%) and can provide results within 30 minutes. However, it is currently not available on Lucira’s website and Amazon once sold.)
At the time of publication, it was difficult to find home antigen tests because the surge in COVID-19 cases led to a surge in demand for them. If you cannot find them online, please call your local pharmacy (these tests are usually available at the front desk).
Abbott BinaxNow COVID-19 antigen self-test sensitivity: 84.6% (PDF) (within 7 days after the onset of symptoms) Specificity: 98.5% (PDF) (within 7 days after the onset of symptoms) The test includes: two costs: $24 Availability: Amazon, CVS, Walmart
Ellume COVID-19 home test (application required) Sensitivity: 95% (PDF) Specificity: 97% (PDF) Test includes: 1 Cost: $35 Availability: Amazon, CVS, Target
Quidel QuickVue Home COVID-19 Test Sensitivity: 84.8% (PDF) Specificity: 99.1% (PDF) The test includes: two costs: $25 Availability: Amazon, Walmart
The key to obtaining reliable antigen test results is frequent testing. “Continuous testing can increase sensitivity,” said Christoper Brooke, an infectious disease expert at the University of Illinois at Urbana-Champaign. “The odds of two negative tests after being infected are much lower than the odds of one negative test.”
The home antigen tests of Abbott, Ellume and Quidel do not require the swab to be pushed into the nasopharyngeal cavity, which you may encounter at the clinical test site, but requires a less penetrating middle nasal swab. Each test has specific instructions and basically requires you to wipe your nose, dip the swab in the solution, transfer some of the solution to a small container, and wait for the result.
After about 15 minutes, you can read the results of the Abbott BinaxNow and Quidel QuickVue tests, just like reading a home pregnancy test: two rows indicate positive results and one row (control) indicates negative results. The very faint second line can still indicate a positive result. The Ellume COVID-19 home test requires a Bluetooth connection to a mobile phone to provide results within 15 minutes through the companion app (iOS, Android). According to the company’s privacy policy, Ellume must provide the public health authorities with the user’s date of birth and their state of residence and postal code, test results, date of test results, and other possible information required by law.
As with all COVID-19 diagnoses (including PCR testing), the collection time of samples for the last known or suspected exposure and/or symptom onset is the biggest factor affecting the accuracy of home antigen test results. For example, this is why Abbott’s BinaxNOW and Quidel’s QuickVue test suites come with two tests designed to be used two to three days apart.
“The sensitivity of the test really depends on when you use it,” said Daniel Larremore, assistant professor of computer science at the University of Colorado at Boulder, who used molecular and antigen tests to simulate the effects of repeated screening in asymptomatic people. The viral load of an infected person changes over time. “When you reach a high enough viral load, the concentration of the antigen will be high enough for testing.” Self-testing the day after attending a party with someone who did not know they had COVID-19 at the time is unlikely to be useful . “No test will be positive for 24 hours after exposure,” Larremore said. If you wait too long for the test, you may miss the peak antigen concentration, which means that if the test detects SARS-CoV-2 antigen in your sample, you should see a darker positive line.
“We usually recommend testing three to five days after exposure,” said McCarthy of Weill Cornell University. If you have symptoms similar to COVID-19, you do not need to wait for the test.
If you are unsure or confused about the results of your home COVID-19 antigen test, please consult your doctor. Whether you should seek confirmatory molecular testing depends on your situation. Larremore said that people should treat a positive antigen test result as a true positive, especially if other factors (such as potential exposure or the appearance of symptoms) support the result. This means quarantining, warning any contacts, and possibly seeking laboratory tests to confirm the results. Seek treatment of symptoms as needed. According to McCarthy of Weill Cornell, if someone has a low level of suspicion of COVID-19 (for example, they are asymptomatic, vaccinated, and/or have no known exposure).
Obtaining a PCR test performed by a laboratory is the best option for accurately diagnosing COVID-19, but an appointment may be difficult to obtain, and sometimes “it takes a long time to get the results, but the results are useless,” said Brooke of American University. Illinois. “Ideally, everyone will perform PCR tests frequently and report the results quickly, but this is obviously impossible. Antigen tests are usually the only truly viable option, so they can play a role in increasing the frequency and scope of testing for the entire population. Very important role.”
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Post time: Sep-17-2021