As COVID-19 cases spread across the state and nation, demand is growing for blood tests to identify people who may have been exposed to the novel coronavirus and developed antibodies to it.
Such antibodies may mean these individuals have at least some immunity to the virus, formally named SARS-CoV2, and therefore may be able to return to work and school — and help jump-start the flagging U.S. economy.
Results may also help identify COVID-19 antibody-positive people whose blood donations could be used to make convalescent plasma, an investigational treatment for seriously ill COVID-19 patients, according to the U.S. Food & Drug Administration (FDA).
But what is antibody testing and is it available?
UCI Health began testing for antibodies to SARS-CoV2 in late April, says Edwin S. Monuki, MD, PhD, head of Pathology and Laboratory Services. Also known as serology tests, the antibody tests must be conducted in a lab certified as meeting federal Clinical Laboratory Improvement Amendments (CLIA), such as the one Monuki directs at UCI Medical Center.
An immune response to the virus
Unlike the ubiquitous swab tests to detect an active COVID-19 infection, a serology test looks at blood for the presence of antibodies, or specific proteins made in response to an infection.
Antibody test results are particularly useful for detecting people who have had a previous infection with few or no symptoms, according to the Centers for Disease Control and Prevention. Experts believe that about 25% or more of people who have been infected with COVID-19 may be asymptomatic.
In the normal course of infection, the body’s immune system attacks and clears a pathogen, then develops antibodies to help fight against reinfection. Antibodies are a response to a virus, not the virus itself.
“Antibodies are produced in the second wave of our body’s response to most infections,” Monuki explains. “Typically, some of these antibodies will directly bind to the virus, then hopefully prevent the virus from binding to and infecting other cells in your body. They’re part of your immune system’s response to infection.”
What does the test involve?
First a blood sample is drawn, either from a vein or a pinprick.
In the lab, red blood cells are separated from the liquid portion of the blood, known as plasma or serum, which contains proteins, electrolytes and hormones, as well as antigens from invading pathogens and the antibodies created to fight them.
These antibodies, which are known as immunoglobulins, are created by the body’s white blood cells to attack and destroy invading antigens and toxins they may produce.
According to the CDC, it takes one to three weeks — longer in some cases — after becoming infected with SARS-CoV-2 for people to make detectable amounts of antibodies. The test is not used to determine whether people have an active infection.
Getting an antibody test
Although it’s unclear whether people will have actual immunity to COVID-19 — or for how long, should the test show the presence of antibodies — many are clamoring to find out.
“Once we announced we had the serology test, we were bombarded with requests,” Monuki says. “We recommend people get the tests at least two weeks after their symptoms started.”
People need a physician’s order for the test and then have their blood drawn at any of the six UCI Health lab service centers, located in Costa Mesa, Irvine, Long Beach, Orange, Tustin and Yorba Linda. Results are usually available within 24 hours. (Insurance can be billed or the patient can pay $42 for the test.)
“With the antibody test, we’re not as worried about shortages as we were with the test to detect the active disease,” Monuki says. “Any patient whose physician orders it can get the antibody test.”
The UCI Health lab has the capacity to handle an expected influx of tests, which is also providing testing for community partners, skilled nursing facilities and first responders, sometimes with the help of its mobile phlebotomists.
Are antibody tests reliable?
As with other tests, the SARS-CoV-2 serology assays aren’t perfect.
Some antibody tests can produce false-positive and false-negative results. But the UCI Health lab offers only tests with low false-positive and false-negative rates.
Monuki says he was initially concerned that someone with antibodies to four other coronaviruses linked to the common cold might confound the SARS-CoV2 test.
“The good news is that we and others across the country have validated these tests. For the reputable ones, it’s not as big a problem as we first feared.”
Immunity not guaranteed
The World Health Organization recently announced that most studies show people who have recovered from COVID-19 do have antibodies to SARS-CoV-2.
It also reported that no study has yet to determine whether these antibodies make people immune from re-infection.
“Antibodies can last in the body for do — perhaps many months and sometimes years,” Monuki says. “But if SARS-CoV-2 is similar to other coronaviruses, it’s likely to be months rather than years.”
More serology research underway
UCI researchers are also conducting other far-reaching serology studies to determine the extent of the virus’ spread among certain communities.
UCI Health infectious disease researchers Philip Felgner, PhD, Saahir Khan, MD, and Sebastian Schubl, MD, are conducting a six-month study of UCI Health workers. Employees will be tested for immune response to SARS-CoV2 antigens along with those of six other harmful coronaviruses known to cause severe respiratory infections.
The COVID-19 Coronavirus Antigen Microarray test involves a simple finger stick blood test and delivers results within 10 minutes. It was developed by Felgner, a professor and director of the Vaccine Research and Development Center at UC Irvine. It may be the most accurate array now available because Felgner has been able to draw on years of extensive coronavirus research.
In addition, the UCI Program in Public Health is partnering with the Orange County Health Care Agency to conduct serology testing of 5,000 Orange County residents for antibodies to SARS-CoV2. The results are expected to better determine at-risk populations and guide local health officials in easing social distancing requirements and allowing businesses to reopen.