Health officials still cautious about factoring in antibody tests
While test could show how many people had virus, it has limits
As businesses and beaches slowly reopen, some health officials are hoping that antibody testing can help detect just how much of the population was actually exposed to the virus during the “first wave.”
But others are still reserved about the accuracy of the tests and cautioned against using them to make decisions on whether it’s safe to roll back restrictions or welcome in visitors.
“We all have this natural curiosity, and it’s such a significant and new disease, so everybody’s really interested if a little sniffle and mild sore throat that they had a month ago could actually be coronavirus,” said Dr. Scott Hoskinson, chairman of the Maui Health Infection Control Team. “But I’m not sure amongst physicians why some consider the IgG antibodies to be so important at the present time, given our lack of knowledge and the inability to really to use it to act one way or another.”
Antibodies are the immune system’s response to a new virus or bacteria. State epidemiologist Dr. Sarah Park explained that when a virus enters the body, it hijacks the cells, reproduces and then goes out in search of other cells to infect. The immune system recognizes the virus and puts up a fight, and in the process, it creates antibodies like IgG, or immunoglobulin G.
“The question really is, which one of these antibodies or proteins is actually protective that basically allows you to be immune to that new pathogen?” Park said in an interview Thursday.
Sometimes, it takes a combination of antibodies to provide protection; in other instances none of the antibodies can offer immunity, Park explained. There’s a wide variety of tests that measure different types of antibodies, but because COVID-19 is still so new, scientists just don’t have enough data to know which of the antibodies can actually help protect against the virus.
“This is the Wild West of antibody testing, so anybody . . . considering doing antibodies really has to be cautious about who is drawing their tests and where they’re sending it and what technique they’re using,” Hoskinson said.
According to the Centers for Disease Control and Prevention, the tests, which require a sample of blood from the patient, can help communities understand how widespread the virus is and identify groups at higher risk for infection. But because they measure the body’s response to the virus, they can’t replace methods like the nasal swab that can directly detect and diagnose an active infection.
“These antibody tests are really not great for the individual person, and really when we talk about it, we’re talking about applying it right now for the population as a whole,” Park said.
Tip of the iceberg
The Department of Health’s Maui District Health Office, however, is interested in what the antibody tests can show.
Sara Hauptman, public health educator with the district office, explained that the virus itself peaks at about 14 days, but the antibodies that are created in response to the virus can stick around for a lot longer, perhaps six months, a decade or for the entirety of someone’s life.
“This is very powerful because we can test for that entire length of time,” Hautpman said Thursday during a news conference.
Use the antibody test too early, and you might not pick up the virus. But use the nasal swab too late, and you may never know the virus had been in someone’s system.
“Why should we do antibody tests? It can’t predict protection right now. It can’t predict if you’re shedding the virus. Why do we do it?” Maui District Health Officer Dr. Lorrin Pang asked. “It’s very, very important, at least to me, and it should be important to everybody as we reopen the economy.”
Pang likened the spread of the virus to an iceberg. Antibody testing can help officials figure out “whether we’ve seen the tip of the iceberg or the whole thing.” He said that it’s a straw man argument to say the test shouldn’t be used just because it can’t predict immunity or whether someone is contagious, things it was never meant to do. While there are questionable tests circulating, there are good ones on the market as well.
“It’s just predicting where are your potential tinderboxes, although ours hasn’t been lit,” he said. “Maui Memorial hospital, we had an outbreak there. I think we should look to see how much was really out there at these kinds of rates that we saw.”
Hauptman said that while the tests cannot show or prove immunity, the data they offer on the prevalence of the virus can help inform decisions on reopening the economy.
“The steps that we want to take forward depend on how much disease is actually in our population, and fortunately, the antibody test is able to give us that information,” she said.
At Maui Medical Group, physicians have been ordering the tests at patients’ request. Administrator Cliff Alakai said that as of Friday, Maui Medical Group had ordered 114 antibody tests. All of the testing goes through Clinical Labs of Hawaii, which uses the Abbott Architect test.
The Abbott Architect test has been rated for its high sensitivity (ability to detect those who had the infection), high specificity (ability to identify those who didn’t) and low false negative rates, according to the U.S. Food and Drug Administration. However, antibody tests can’t indicate current active infection or confirm immunity, and insurance coverage is inconsistent or nonexistent for the tests, which cost about $45 out of pocket, said Dr. Guy Hirayama.
The tests, Hirayama said, are “more for epidemiologic population analysis for exposure and possible immunity prevalence. Not yet enough information to reliably be used to indicate immunity and safety for return to work.”
“We will order the test if the patient wants the test, but at this time, we can’t see the value of the test, which is why HMSA and Kaiser are not paying for the test as a covered benefit,” Alakai added.
Last week, a Maui Health employee received an antibody test from a community provider that detected antibodies. The employee was given a swab test that also confirmed that they had active virus.
Dr. Michael Shea, ICU medical director and physician lead for the hospital’s Emergency Operations Center, explained that because the employee didn’t have symptoms, it was hard to know where they were in the stage of their illness. The swab test helped indicate that the virus was still around, though it didn’t necessarily mean they were contagious.
If another employee or patient tested positive for antibodies in the future, the hospital would swab them, too, Shea said.
In the meantime, the hospital is not using the antibody test to make clinical decisions, Hoskinson said. Even if employees were to test positive for antibodies, it wouldn’t mean that they were automatically immune and could work on the front lines of the emergency room or COVID units without protective equipment.
“We just don’t know enough about it,” he said. “So antibody testing for our health care employees is of no value to us infection control wise. We consider everybody still susceptible even if they have IgG antibodies.”
As antibody tests become more common, Park expects the number of positive cases to grow but not significantly based on how the state has fared so far. As of Friday, labs across Hawaii had tested 54,014 people and reported 649 positive cases, according to DOH data. That means about 1.2 percent of people who’ve been tested have been positive, though that number could change as antibody tests are deployed.
“What I suspect will happen is that if we really look, there’ll be pockets of the community, of various communities throughout our state, where there may be a slightly higher percentage that were actually exposed to the virus,” Park said. “This is actually something from the state perspective we’re very much interested in.”
Park said because of the questions surrounding the antibody tests, the state is not counting them toward positive case counts unless the person has also tested positive through a swab test.
It’s for the same reasons that Shea and Hoskinson were cautious about using the test to decide whether it’s safe for visitors to return or for residents to gather in large groups again.
“People want to feel safe, and that’s why they want to get this test as an individual,” Shea said. “I think if anything, it may give them a false sense of security, and that’s what we want to avoid. At this point we’re still learning so much about this virus, and the science is evolving on an almost daily basis. . . . The test is not reliable enough for us to make any decisions on an individual basis.”
* Colleen Uechi can be reached at firstname.lastname@example.org.