Covid Testing: What You Have to Know

Virus tests are categorized based on what they are looking for: molecular tests that look for the genetic material of the virus and antigen tests that look for viral proteins. The various tests use a sample from the nose, throat, or mouth that can be sent to a laboratory or processed within minutes. Testing should be free or paid for by your insurance company, although some testing centers charge additional fees. Here are the general tests and some of the pros and cons of each.

Molecular laboratory test: The most widely used test that most people get is the PCR or polymerase chain reaction test, a technique that looks for pieces of the virus’ genetic material – much like a detective looking for DNA at a crime scene.

Pros: This test is considered the gold standard for coronavirus testing because it can detect even very small amounts of viral material. A positive result from a PCR test almost certainly means that you are infected with the virus.

Disadvantages: Since these tests have to go through a laboratory, the typical turnaround time is one to three days. However, it may take 10 days or more to see results. This can limit the usefulness of this test as you may have viruses spreading while waiting for this period. As with all coronavirus tests, a PCR test can give a false negative result in the first few days after infection because the virus has not reached any detectable levels. (One study showed that in people who were subjected to PCR testing three days after symptoms began, 20 percent still showed a false negative.) Another frustration with PCR testing is that they sometimes use the leftover genetic material of the virus weeks after a person’s recovery and no longer contagious. The tests are also expensive, costing hospitals and insurers $ 50 to $ 150 per test.

Rapid antigen test: An antigen test looks for pieces of coronavirus proteins. Some antigen tests work similarly to a pregnancy test. If virus antigens are detected in the sample, a line on a paper test strip will turn dark.

Pros: Antigen testing is some of the cheapest (only $ 5) and fastest testing, and can give results in about 15 to 30 minutes. Some college campuses and nursing homes use rapid tests almost daily to screen people and catch many infectious people before they spread the virus. Antigen tests work best when done a few times a week, rather than just once. “It tells you, am I at risk for my family right now? Am I currently spreading the virus? “said Dr. Michael Mina, an epidemiologist at Harvard University’s School of Public Health and a proponent of widespread rapid tests. He cautioned, however,” If the test is negative, it doesn’t tell you if you are contagious tomorrow or if you were contagious last week were.”

Cons: Antigen testing is less likely than PCR to find the virus early in the course of infection. One concern is that a negative rapid test result will be viewed as a free pass to reckless behavior – like wearing a mask or attending an indoor meeting. (The Rose Garden event at the White House is a good example of how quick tests can create a false sense of security.) A negative antigen test doesn’t tell you for sure that you don’t have the coronavirus – it just tells you that no, since antigens have been detected, you are unlikely to be highly contagious today. (In one study, a rapid antigen test missed 20 percent of coronavirus infections found in a slower lab PCR test.) Antigen tests also have a higher rate of false positives. Therefore a positive rapid test should be confirmed.

Fast molecular test. Some tests combine the reliability of molecular tests with the quick results of a rapid test. Abbotts ID Now and the Cepheid Xpert Xpress are based on a portable device that can perform a molecular test right in front of you in minutes.

Pros: These tests are quick and highly sensitive and can identify those who are exposed to coronavirus about a day earlier in the course of an infection than a rapid antigen test. A rapid molecular test is not as accurate as the laboratory version, but you will get the result very quickly

Cons: Depending on where you live, rapid molecular tests may not be widely available. They are also less convenient and often slower than many antigen tests. And, as with all coronavirus tests, a negative result isn’t a guarantee that you don’t have the virus. Therefore, you still need to take precautionary measures. Like its cousin in the laboratory, a rapid molecular test can detect genetic material residues of the virus even after you have recovered.

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