Why this matters. As the nation works to save lives and flatten the curve of COVID-19 cases, widespread testing could help reduce the death rate, help identify those who should self-isolate, and help businesses recover. There are challenges, however, associated with the use and availability of tests, as well as with determining their accuracy. What is it? There are currently three types of tests for COVID-19: molecular, antigen, and serology. Molecular tests and a new antigen test help diagnose active COVID-19 infections, and serology tests help determine whether someone was previously exposed to the novel coronavirus, which causes COVID-19. How does it work? While each kind of test takes a different approach, they all collect vital information about exposure to the virus. Molecular tests amplify and detect genetic material from novel coronavirus in a sample taken from a patient's saliva, nose, or throat to determine whether there is an active infection (fig. 1). For example, molecular tests based on the polymerase chain reaction (PCR) use a genetic photocopier, copying a unique portion of the coronavirus genetic material, if present, until there are enough copies to detect. Antigen tests can detect the virus by binding parts of the virus, called antigens, to a membrane. Antibodies that can fluoresce are also added to the membrane. If enough antigen is present to bind to the antibodies, the total fluorescence from the antibodies becomes high enough to indicate a positive result. Serology tests, which typically require a sample of blood from a patient, can detect the presence of antibodies produced by a patient's immune system in response to the coronavirus (fig. 1). Such antibodies can persist in the blood after a patient recovers from an infection. Thus, a positive serology test result indicates prior exposure to the novel coronavirus but does not necessarily mean that the patient is still infected. How mature is it? All three kinds of COVID-19 tests are commercially available under the Food and Drug Administration's (FDA's) emergency use authorization (EUA), which allows for the use of certain unapproved medical products or unapproved uses of approved medical products under certain circumstances during a public health emergency. As of May 13, 2020, FDA has authorized at least 56 molecular tests for COVID-19 via EUA; these tests generally rely on PCR technology. Devices used for administering molecular tests range in size from larger equipment to smaller, portable devices that can be used on-site near the patient. On May 8, 2020, FDA authorized the first antigen test for COVID-19 via EUA. According to FDA, antigen tests, which can be run in minutes, have a higher chance of false negatives compared to molecular tests. FDA states that negative antigen test results may need to be confirmed with a molecular test before making treatment decisions. As of May 13, 2020, FDA has authorized at least 12 serology tests for COVID-19 via EUA. For COVID-19, serology tests were first authorized by FDA about a month after molecular tests were authorized. Devices used to administer serology tests also range in size, with some about the size of an over-the-counter pregnancy test.
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1 online resource (1 PDF file (2 unnumbered pages))