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Fox News medical contributor Dr. Marc Siegel joined "Tucker Carlson Tonight" Thursday to break down the latest developments in the fight against the coronavirus after the Food and Drug Administration (FDA) authorized the first rapid coronavirus blood test that measures antibodies and immunity.

"This is called point-of-care testing," Siegel explained. "Rapid testing that can give you results in just a few minutes. There are a few different kinds of tests, one where you test for the virus itself. We know that from the swabs. The other [is] where you do a blood test, you test for immunity."

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Siegel's comments come hours after Cellex Inc. received emergency authorization for its test which examines the number of antibodies in the blood and whether an individual has developed immunity to the COVID-19 virus.

"Cellex was approved for emergency usage to see whether we can tell who has had this virus and who's immune to it, so they can go back go back into society, but we are not entirely there yet," Siegel cautioned.

Siegel said he had contacted Adm. Brett Giroir, the assistant secretary for health at the U.S. Department of Health and Human Services (HHS), who acknowledged that "the tests that we have already, the ones that are on the big mobile units that require all of this protective equipment, they have a one out of three rate of not getting it right.

"They say you don’t have the virus when you actually do," Siegel added.

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Siegel said Giroir prefers the test developed by medical device company Abbott, which uses the company's portable ID NOW platform and does not require a central lab for analysis, saving precious time for medical workers and patients.

That test allows doctors to swab someone's nose or throat, insert the swab into a machine, and receive getting results in five to 15 minutes (results can take longer if a sample tests negative, but can take only five minutes if the person tests positive).

"That is another point-of-care test that says, 'You have the virus' [or] 'You don’t have the virus,'" Siegel said. "As you might imagine, if I can figure out who had the virus I can figure out who has it and flatten the curve.

"That [Abbott] test -- this is breaking news -- is already around the country in 1,800 different tiny boxes that we only use for the flu that we can now use for coronavirus. It’s ready to go," added Siegel.

On Thursday, President Trump tested negative for coronavirus for a second time. According to White House Dr. Sean Conley, the president had been tested by the Abbott rapid point-of-care test and the results were delivered in 15 minutes.

Fox News' Christopher Carbone contributed to this report.