Coronavirus Testing: What is a COVID-19 genetic, antigen and antibody test?

ByReggie Aqui via WABC logo
Tuesday, May 19, 2020
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There has been a lot of talk about testing for the coronavirus, but you may not entirely understand what the different tests are for.

SAN FRANCISCO -- There has been a lot of talk about testing for the coronavirus, but you may not entirely understand what the different tests are for.

The coronavirus makes some people sick, some people don't know they have it and spread it, and, for others, the virus is deadly. But how do you know if you're infected?

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"The test that tells you if you are infected or not, the one that uses the cotton swab, is a test that looks for the viruses' genetic material," said Dr. Alok Patel, part of ABC7 News team of coronavirus experts.

That cotton swab collects a sample from the back of your throat, and up your nose. That's where the virus likes to hang out. The sample is then sent to a lab for analysis.

"And it compares the sample that the doctor would get on a swab to a known sample of the virus' genetic material and it looks for a match," said Dr. Patel.

If there is a match, you have the coronavirus.

"If you test negative, you could be free of it and not have the coronavirus, or the samples may not have caught the virus's genetic material," said Dr. Patel.

It takes three to five days to get the results of a genetic swab test.

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An antigen test would take minutes.

"An antigen test is going to look for proteins on the surface of the virus instead of looking for the genetic material inside the virus," said Dr. Patel.

There is no antigen test currently available.

"The hope is we will soon, so people can get rapid results while going to the doctor's office, or the clinic, and know immediately whether or not they have coronavirus," said Dr. Patel

The other test everyone is talking about is the antibody, or serological test. This is blood test that will tell you if you've already been infected with the coronavirus and recovered.

"What the antibody test is looking for is antibodies in your blood. So if you get a virus or infection, your immune system is going make antibodies, and these antibodies are little proteins that will help you fight off the infection if your body ever sees it again," said Dr. Patel.

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If you have antibodies, you may be able to fend off the coronavirus if you are exposed to it in the future.

"It takes about a week or two after an infection for your body to build up antibodies," said Dr. Patel.

What we don't know is how long that immunity will last.

"But based on everything we know from the previous SARS virus, the one that is related from this coronavirus, immunity should last at least a couple of years, but again we still need to get more data to figure this out," said Dr. Patel.

There are only a handful of antibody tests approved by the Food and Drug Administration.

Getting an accurate result is important in determining who may be able to donate blood plasma to help people who are severely ill with COVID-19.

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"And donate antibodies to help other people recover faster," said Dr. Patel.

An antibody test would also be helpful in determining herd immunity.

"Which is where enough people in the population have immunity against this coronavirus that the virus can no longer spread from human to human," said Dr. Patel.

Getting herd immunity can only happen with the development of a vaccine, stopping the spread of the coronavirus in its tracks.