Pre-selected participants, who were selected based on a random sample, will be checked for immunity against the virus.
The county announced Thursday the pilot test program will involve 1,000 new adults who will be tested every two weeks to track the virus. For those not selected to take part, officials caution paying a private lab to conduct the test.
"There's no way for us to regulate the private entities that do this," Los Angeles Mayor Eric Garcetti said during a daily press conference.
The study's goal is to determine the likely number of people in the county who already contracted coronavirus. Knowing this critical information will reveal a more accurate picture of how widely the virus has spread in the population, the mortality rate and potential immunity.
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Dr. Neeraj Sood with USC Sol Price School of Public Policy partnered with the Los Angeles County Department of Public Health to hold the testing at six undisclosed locations.
Sood explained the importance of the testing.
"Five patients who had COVID and who are on ventilators have the most severe form of the disease. They took antibodies from the blood of people who had recovered from COVID and then they injected these antibodies into these five patients. These five patients saw a remarkable improvement in their clinical trials," he said.
Sood hopes to start phase two, which involves setting up sites across the city to test for the virus on a larger scale.
He has already raised $100,000 to conduct more research on coronavirus.
There are currently two different types of tests for COVID-19. One is a swab test -- also known as the PCR test, which saw a shortage due to the high demand -- and the other is a blood test. There is currently a 14,000 swab test backlog at California labs.
The antibody blood test is in less demand as it does not determine if someone has the virus.
"It's not a dependable test to know whether or not you can affect others. It's a good test to know whether you've had it," Garcetti said.
In addition to USC-LA County's research testing, the HOT Clinic of Encino conducted its own antibody testing in the parking lot of the Monta Factory Restaurant in Glendale on Thursday.
"We currently administer this test in our clinic, some of the limitations is we can't have too many people in at a time and keep safe social distancing," said Edward Zaghikian, operations manager of the HOT Clinic.
It's called a serologic test, for blood serum, and it will be a key in someday allowing an end to stay-at-home orders.
"We know that around the globe, the use of serologic testing is being discussed," said Dr. Mark Ghaly, secretary of the California Department of Health and Human Services.
Public health experts hope that mass screening with antibody tests could eventually help track how the virus spreads and who might have built up immunity.
Dr. Anthony Fauci, the nation's leading infectious disease expert, said the U.S. is days away from having a large number of antibody tests available.
"But they need to be validated," he said during a CNN interview Friday. "You need to make sure they're consistent and that they're accurate."
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The FDA is permitting companies to launch certain types of finger-prick tests that can detect whether people may have recently been infected.
At Stanford University, researchers have already begun testing more than 3,000 people.
"I think this (study) has very important implications for how we understand the epidemic, for how we move it forward," Stanford's Dr. Eran Bendavid told ABC News' Diane Sawyer. "From our survey really the most important piece of information is, how many people in our country have been infected?"
Warner Thomas, CEO of the New Orleans-based Ochsner Health System, and Ochsner's chief medical officer, Robert Hart, also said they expect antibody testing to be available in a couple of weeks.
"We look forward to being one of the first centers in the country that will be doing antibody testing," Thomas said during a telephone news conference Thursday.
It was not immediately clear how many tests would initially be available.