Antibody tests aren’t always reliable or available. But businesses are racing to use them

Laurence Darmiento
Los Angeles Times

A full-service hotel is a complex business even without a pandemic upending society. Guests eat, sleep and play in close contact with hundreds or more people, including workers who feed them, clean their rooms and run what amounts to a small city.

So when stay-at-home-orders are lifted and the Hilton Universal City Hotel near Los Angeles fully reopens, guests and newly called back workers will encounter safety measures to keep the coronavirus at bay, including masks, social distancing and, for workers, temperature checks at the door.

COVID-19 antibody tests have been touted as a way to give people so-called “immunity passports” that would allow them to hold jobs without worrying they are contagious, but scientists are unsure how much protection they provide.

The hotel adjacent to now-closed Universal Studios Hollywood is currently operating with a skeleton staff that already has instituted a heightened safety regime. But as occupancy grows there will be one thing neither workers nor guests should expect to provide: clinical proof that they are not a threat to those around them, shown with test results indicating they already were exposed to the virus and now have antibodies that could protect them from reinfection.

“We will not go to that step. We don’t feel the appropriate authorities are going to put up testing stations on every block for commerce to open back up,” said Mark Davis, chief executive of Sun Hill Properties, which manages the hotel. “That’s unrealistic.”

Antibody tests have been touted as a way to provide people with so-called “immunity passports” that would allow them to hold jobs without worrying they are contagious. And while many businesses seek them, the reality is that while production is growing the tests are not yet commonplace, and even the best among them will not provide all the answers businesses want.

Public health officials are using them to get a more accurate picture of the virus’ prevalence in communities, but relying on them to screen individual workers exposes the tests’ shortcomings: Not only can the tests give false positives and negatives, but scientists don’t yet know how much protection the antibodies even provide — or for how long.

Last month, the World Health Organization went so far as to warn governments against issuing immunity passports because there is currently no proof that antibodies can protect patients from being reinfected. While many scientists are optimistic since other coronaviruses such as SARS created powerful immune responses, not all diseases do and the science is not there yet.

“We are sort of building the car as we are driving it. We are talking about making society-level decisions on the basis of lab testing, and as a person who does lab testing for a living that really makes me nervous,” said Susan Butler-Wu, associate professor of clinical pathology at USC’s Keck School of Medicine.

Questions linger about the reliability of tests now on the market, including from China, that detect virus-fighting proteins in the blood formed in response to an infection. U.S. public health labs and established private companies, such as LabCorp. and Quest Diagnostics, are developing and expanding their antibody testing capabilities. But the tests won’t be available on a mass scale before states reopen their economies, already beginning in fits and starts across the nation.

The tests are different from PCR tests, which show whether a person has an active infection. After a slow start, the U.S. is ramping up its PCR testing capacity, though even these tests are not easily accessible to everyone. CVS announced its stores will be offering the tests free of charge nationwide and L.A. Mayor Eric Garcetti announcing a plan last week to make them free to all Los Angeles County residents.

PCR tests will be needed by businesses to keep sick workers at home, but they don’t hold the promise of antibody tests, which can show a person fought off the virus but perhaps wasn’t even aware of it due to having mild or no systems — possibly 25% of the population by one government estimate.

The shortcomings of current antibody testing were laid out in a review released April 22 by the Bloomberg School of Public Health at Johns Hopkins, which concluded that using the tests to create “immunity certificates” either by government or business was “not a justifiable step at this time.”

One complication is that there are multiple versions of the tests, including rapid diagnostic tests similar to home pregnancy kits that simply detect the presence of antibodies. More sophisticated tests can determine the level of antibodies or even whether a patient’s antibodies actually kill the virus.

Those most advanced tests, which are not yet commercially available, can take nearly a week and are processed at labs that need to operate at high biosafety levels since they use cell cultures with live viruses. But even these tests can’t show how long a patient may retain immunity, which would require the results of studies done over time.

“We are presuming that people who have had the disease and recovered, that they have some level of immunity for some period of time,” said report coauthor Gigi Gronvall, an associate professor at the Bloomberg School, who is optimistic studies will confirm this. “But it’s really hard to say ‘You’re good to go.’”

Confounding the matter are scores of tests that hit the U.S. market after the Food and Drug Administration allowed companies to sell their products following self-certification of their accuracy. On Monday, in response to a swarm of unreliable tests, the FDA announced that commercial test makers have 10 days to submit test data and apply for a so-called Emergency Use Authorization or face removal from the market. The data must show the tests can capture the presence of antibodies at least 90% of the time, while having a false positive rate of no higher than 5%.

The FDA said it is already reviewing more than 200 antibody tests from manufacturers, but as of Monday only a dozen had been issued the authorizations. That has given businesses seeking to reopen little to work with.

The White House issued a report last week noting that antibody testing will play a key role in returning the country to normalcy and said it is exploring a strategy of giving two tests to each person under certain circumstances, which can sharply improve the so-called predictive value of the tests. The FDA also issued guidance last week suggesting a second screening using a test from a different test maker in the case of a positive result.

Thorny issues remain, however, including the costs of mass testing and who will foot the bill. Some antibody tests have been priced at well over $100, but economies of scale could bring prices down to $75 for broad workplace testing. And then there are the medical privacy rights afforded workers through a variety of federal laws, which typically would not allow employers to take the temperature of workers or require them to submit to testing.

However, because there is a declared pandemic, the federal Equal Employment Opportunity Commission has issued guidelines allowing such intrusions. Experts warn, though, that doesn’t mean that other provisions of employment laws are no longer in force. “We always have to remind employers in these conversations that all the laws are not out the window,” said Wade Symons, leader of the regulatory resource group at Mercer, a human resources consulting firm.

Given the unreliability of some of the tests on the market, there is a practical worry: Positive test results could give people a false sense of security when the test is wrong.

“We are not factoring in human nature. How rigorous and careful are you going to be about social distancing, with disinfecting, with all of these things, if you in the back of your mind know that you have a quote unquote positive test?” noted USC’s Butler-Wu.