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Some of the tests look for part of the viral genome (molecular tests). Other tests – some of the newest ones that are coming out that are more rapid – test the blood for antibodies of the virus (serology tests).
The first test, if positive, tells you the virus is onboard – you’re currently infected. The second type of test tells you that you’ve been exposed to COVID-19 virus, whether you are currently infected, or if you have been infected and cleared the virus.
After your symptoms have remitted, it takes two of the first kind of test administered 24 hours apart with nasopharyngeal swabs to test negative for the virus to be reasonably sure it has cleared your system.
Still, there are outliers that this test may not catch. I haven’t seen data for COVID-19 immunity post-infection, but in general, once you’re infected with a corona-type virus, you are protected from that particular strain for at least a while, and usually you don’t come down with it again.
Did the CDC work out its COVID-19 test accuracy problems?
In February, the CDC decided the virus DNA test needed a legal designation for widespread use under emergency authorization, according to the American Association of Medical Colleges (AAMC), a non-profit that administers tests to medical students and advocates for medical schools, students and patients in Washington, D.C.
Shortly thereafter, the CDC announced the tests had accuracy problems, meaning some results already returned were useless, the AAMC states. The replacement kits took two weeks to come. Meanwhile, academic researchers had new tests they developed that the law prevented them from administering to the public, the AAMC states.
The FDA March 11 approved a second type of test developed by the New York State Health Department for use in diagnosing COVID-19 throughout the country. The FDA has gone on to approve COVID-19 test kits for commercial use; they are as follows:
- Nucleic acid detection kit, manufactured by Shanghai GenoeDx Biotech Co. Ltd.-Shanghai, China. It is distributed by S&S Enterprise.
- Novel coronavirus 2019 nucleic acid detection kit (fluorescence PCR method), manufactured by Beijing Applied Biological Technologies Co. Ltd. It is distributed by Sahar International.
- AllplexTM 2019-nCoV Assay, manufactured by Seegene Inc. – Seoul, South Korea. It is distributed by Endure Medical Inc.
- SOLGENT DiaPlexQ Novel Coronavirus (2019-nCoV) Detection Kit, manufactured by Solgent Co. Ltd – 3F, 32, Techno 6-ro, Yuseong-gu, Daejeon, South Korea. It is distributed by Wellness Pro Inc.
According to the U.S. Centers for Disease Control and Prevention, the public health testing labs that analyze the samples in COVID-19 tests all receive supplies through the CDC, which provides reagents (chemicals needed in the course of the DNA analysis of the virus). Commercial labs get the COVID-19 testing materials they need from the U.S. Food and Drug Administration.
The CDC's test for viral DNA is a polymerase chain reaction test, which is used to identify DNA in all sorts of contexts, including the criminal justice system, genomics, and other disease testing.
The tests also require RNA material from the SARS-CoV-2 virus that causes the COVID-19 coronavirus disease. This allows the tests to identify potential virus genes in swab samples from the respiratory tract, according to the CDC.
Ideally, the AAMC states, problems with COVID-19 test accuracy are largely solved as of this MedicineNet article’s publication date of March 27, 2020. Other tests are under review and may get early FDA approval for use in this pandemic.
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