Best At-Home COVID Tests 2021
ConsumerLab - There has been much confusion and about tests for coronavirus and the FDA has reported that some test developers have falsely claimed their tests are FDA approved or authorized and that many commercial tests are performing poorly, so it is important to sort out the facts. .
Update on Omicron variant: According to the WHO, current SARS-CoV-2 PCR diagnostics continue to detect this variant. Several labs have indicated that for one widely used PCR test, one of the three target genes is not detected (called S gene dropout or S gene target failure) and this test can therefore be used as marker for this variant, pending sequencing confirmation. Using this approach, this variant has been detected at faster rates than previous surges in infection, suggesting that this variant may have a growth advantage.Before we get into specifics, let's start with a quick overview of the types of tests for coronavirus.
There are basically two types of tests for the coronavirus that causes COVID-19:
This test detects the (SARS-CoV-2) to determine if you have an active infection and are infectious, i.e., you can spread the virus. Although you can be infectious before showing any symptoms, the virus is best detected during the first week of symptoms (which is about two weeks after becoming infected from exposure) (Sethuraman, JAMA 2020).
The virus test is best done by collecting a sample of (typically from the nasopharynx or nostril) or . There are two type of virus tests: the PCR and antigen test. Both tests need to be analyzed in a laboratory or with a special rapid, portable machine.
The uses a technique that amplifies genetic material (RNA) from the virus. This can take as little as a few minutes or several hours. The FDA has begun allowing some at-home sampling kits to be sold by which you can collect your own sample and drop it off or mail it to a lab, which will report the results back to you.
An analysis of tests performed among symptomatic and asymptomatic patients at Vanderbilt University Medical Center showed that the proportion of samples testing positive on PCR tests were twice as high at 2 pm than in the morning, decreasing later in the afternoon and evening. Researchers proposed this may indicate that test accuracy varies by time of day and could have public health implications (McNaughton, medRxiv 2021 -- preprint).
Update: In addition to the many commercial PCR tests that have received Emergency Use Authorization from the FDA, the CDC has been producing its own, FDA-authorized, PCR test. More recently, the CDC developed a newer test that can simultaneously test for and distinguish between COVID, influenza A and influenza B, and, as of January 1, 2022, it will withdraw the older test.
Several home antigen tests are now sold, including Abbott BinaxNow Self Test, Quidel QuickVue, Flowflex, and InteliSwab. There appears to be a significant difference in the accuracy of these tests.
This test detects to the virus and requires — either a drop or a vial — to determine if you have been infected in the past and have developed some level of immunity. This test (also called a serology test) can be run in a laboratory or on a test strip, although even test strips must be used in an authorized facility, not at home.
As it takes time to develop antibodies that can be detected, antibody tests are most accurate when performed at least 20 days after the first disease symptoms and may be most accurate (in terms of not missing antibodies that are present) 4 months or longer after a positive virus test. Although it is not recommended that antibody tests be relied upon to determine the effectiveness of vaccines, be aware that because the authorized vaccines generate antibodies only to spike proteins. A although it would suggest that a person has not had COVD-19. The list of authorized antibody tests below indicates whether a test focuses on spike, nucleocapsid, or both types of proteins.
Tests focus on levels of the antibody IgG, which persists without much decline for several weeks, but may include levels of IgM which fall off more rapidly (Sethuraman, JAMA 2020). These tests look for antibodies to specific parts of the virus, namely its (proteins on the outside of the virus that can bind to receptors on human cells) or (proteins inside the virus). An advantage to testing for antibodies to the nucleocapsid is that these antibodies can be easier to detect, however, antibodies to the spike proteins are believed to be more important in conferring immunity against the virus, as these antibodies may block viral entry into cells — although antibodies to nucleocapsid proteins may still serve as proxies for immunity.
If, at some point, tests for spike protein antibodies are indicated , those that provide a quantitative or semi-quantitative measurement, will be more useful than those that provide only a yes/no answer.
Some labs may provide you with an that reflects the strength of the antibody signal produced from your test. Higher antibody levels generate higher signals and higher index values. The interpretation of these index values depends on the test used. For example, for a particular test the cut-offs could be "less than 1.01" for negative, "1.01 to less than 1.21" for indeterminate, and "greater than or equal to 1.21" for positive (Theel, J Clin Microbio 2020). Or, there could just be a single cut-off index value of, say, 1.40 for positive, with anything below being negative (Example: Abbott Alinity -- https://www.fda.gov/media/137910/download). If you would like to know your index value, be sure to check that the lab you use provides the value.
To speed the availability of tests, rather than put these through its normal approval process, the FDA has provided a special emergency use allowance (EUA) for tests that, although imperfect, may be useful at this time. So there are actually no FDA "approved" SARS-CoV-2 virus tests, but a list of "FDA authorized" tests. The FDA allowances are based on data submitted by the test manufacturers, but the National Institutes of Health (NIH) and other government laboratories are now conducting independent tests of these tests and the FDA has been making the results public.
Be aware that in June 2020 the FDA warned consumers about at-home antibody tests being sold without FDA clearance or approval and issued warning letters to three companies selling these tests. Some of these tests were falsely labeled as FDA approved.