An antibody test to identify people who have recovered from the COVID-19 infection was developed by the New York State Department of Health, according to an announcement by Governor Andrew Cuomo on Tuesday.
As opposed to diagnostic tests, which often work by identifying genetic material specific to the virus, antibody tests detect the amount of antibodies present in an individual's blood. They measure the body's immune response rather than the presence of the virus itself.
Antibody tests, or serological tests, can be used to diagnose, but they are not the first line in diagnostic testing because they may not catch the virus early when the immune response is just beginning.
Governor Cuomo said that the Department of Health approved the new test for use in New York State, but that it has to be brought to scale first.
"You have 19 million people in the state of New York, just think of how many people you would need to be able to test and test quickly," he said in the announcement.
The primary goal of antibody testing is to identify people who have recovered from the virus, with the expectation that these people have developed a sufficient amount of antibodies to help them fight off another infection. The hope is that antibody tests — if they are produced on a large scale — will stimulate the economy by getting the people deemed immune back to work.
The U.S. Food and Drug Administration (FDA) issued a policy on antibody testing in March, allowing some developers to market or use tests without FDA review if they met certain conditions. Under the Emergency Use Authorization (EUA), the FDA has authorized only one EUA for a serological test, which is intended to be used in clinical laboratories.
Since then, the FDA said they are aware of more than 70 test developers who have reached out to the FDA to say they have tests available for use. However, the FDA announced that some developers are making false claims that their tests have FDA approval or authorization, or that they can diagnose people with COVID-19, according to a press release the FDA released on Tuesday.
Regarding the influx of antibody testing developers, White House coronavirus task force response coordinator Dr. Deborah Birx urged Americans not to buy antibody tests online.
"If you see them on the internet, do not buy them until we can give you a test that's reliable for all Americans," she said in a coronavirus press briefing on Tuesday. "Some of the tests that may be available on the internet may have very low sensitivity and specificity and give you a false reassurance that either give you a false positive or a false negative implying that you may be protected."