A new kind of coronavirus test is coming: fast, easy, (relatively) cheap, and could soon be available at an airport or school near you.
That’s the vision for rapid antigen tests, anyway. It’s shared by manufacturers, the Trump administration, businesses that want customers to feel safer. The Pac-12 athletic conference has pinned its football-season hopes on the tests helping to catch the virus before it spreads through locker rooms or to opposing sidelines.
The federal Food and Drug Administration (FDA) has authorized the use of four antigen tests on an emergency basis, through a limited and less rigorous process than is typical for full FDA approval. Millions of them are shipping across the country, and they typically produce results within five to 15 minutes.
There’s a tradeoff, though, for the speedy tests. Experts say they’re not as accurate because they’re less sensitive to the virus than the current standard.
As the Pac-12 begins its shortened football season, University of Washington athletes will be among the first to give the emerging technology an extended spin.
The conference believes more, if less accurate, testing could help drive down transmission of the virus that causes COVID-19 because “you’ll get people before they’re infectious and pull them out of the pool,” said Dr. Kim Harmon, a UW team physician and a member of the Pac-12’s COVID-19 Medical Advisory Committee. “By aggressively searching for people who are asymptomatic, you won’t get spread.”
But this testing theory is, itself, untested.
“We’re building the airplane as we’re flying it,” Harmon said.
And while many experts view the Pac-12’s plan as a sensible way to return athletes to the field, questions remain over how effectively these tests will catch the virus in patients without symptoms.
“There’s no data that shows this works,” said Dr. Geoff Baird, the acting chair of the UW’s Department of Laboratory Medicine. Baird views implementing an unproven strategy on students as too risky.
The new coronavirus has propelled the urgency of discovery beyond science’s typical pace. As the Pac-12 forges into unknown terrain, its actions will reveal these tests’ strengths, weaknesses and unknown features, and the data collected from athletes could mark a new path forward.
How the tests work
Think of a pregnancy test: A little urine on a test strip, biochemistry and a few minutes’ time produce a faint symbol that changes everything.
They’re effective, but not infallible.
Rapid antigen tests for the new coronavirus (whose official name is SARS-CoV-2) work similarly, said Dr. Gary Procop, the director of clinical virology at the Cleveland Clinic.
Much as pregnancy tests detect a particular hormone, these tests seek to identify specific antigens, or proteins, produced by the virus.
Samples from a person’s nostrils are transferred to a testing cartridge, which contains a test strip embedded with antibodies. If the antibodies join with antigens from the coronavirus, they’ll stick like a “lock and key,” Procop said. Then, a third protein on the testing strip prompts a glow or change in color, and a machine reads the strip and produces a positive or negative result.
PAC-12 commissioner Larry Scott called this method a “game changer.”
The conference plans to test its athletes daily using technology from Quidel, a publicly traded health care diagnostics company. Athletes who test positive will receive a second test for confirmation.
The athletes also will receive a weekly PCR (polymerase chain reaction) test.
PCR tests — the kind used to diagnose President Donald Trump — amplify and measure the virus’s genetic code. They’re more expensive and take longer, but they’re also more sensitive, offering a lower threshold for detecting the virus.
With antigen tests, “you’re sacrificing accuracy for speed,” said Kelly Wroblewski, director of infectious diseases for the Association of Public Health Laboratories.
The Pac-12 hopes daily antigen testing will spot when viral loads begin to spike within the body, which usually happens a few days after infection and can come before someone experiences symptoms.
In its emergency use documentation, Quidel claims its antigen test agrees with PCR results 99.5% of the time. In a clinical performance study of 209 patients with symptoms of COVID-19, the Quidel test missed one of 30 patients the PCR test considered positive. Other antigen tests have performed similarly, according to documents submitted to the FDA.
But how these tests perform among asymptomatic patients, in the field or in independent evaluation is not well-studied. Evaluating a test like this could take years, Wroblewski said, and “we don’t have years.”
Experts say it’s possible the tests could miss antigens in samples with lower concentrations of virus. And in largely healthy populations with a low prevalence of the virus — such as a football team — Procop said “more of your positives are likely to be false positives than true positives.”
Weekly PCR testing is expected to help with quality control.
“If there’s 1,500 football players getting tested a week, we’ll have 1,500 concurrent samples and can figure out if our theories are correct or not,” Harmon said. “If there are problems with false positives or negatives, we’ll have to figure it out.”
Harmon says preliminary data has provided some confidence.
The University of Arizona has used Quidel antigen tests with relatively reliable results since May, said David Harris, the executive director of the university’s Health Sciences Biorepository.
About 35,000 tests have been administered to athletes and other students. University scientists compared 1,900 results with PCR tests. Positive results matched around 92% of the time, for both symptomatic and asymptomatic cases, Harris said. Campus health researchers are preparing a paper.
“We feel very confident the antigen test provides us with a very reasonable assurance whether somebody is infected or not,” Harris said.
Harris presented some of his findings to Pac-12 officials and member schools, and said he met some hesitation from universities who hadn’t run their own tests.
“If you’re not satisfied, find another test,” he said. “If you can’t find another test and you’re not satisfied, pull the covers over your head and just wait.”
Daily antigen testing could be most useful in catching people who are pre-symptomatic and may be contagious, even if it won’t “catch everyone who has the virus and keep them from the field,” said Omai Garner, the director of point of care testing at the UCLA Department of Pathology and Laboratory Medicine.
“The math and modeling suggest it will work,” said Garner, who added he was not making a judgment about the data.
Wroblewski said antigen testing is best used not for screening but as a diagnostic tool in symptomatic populations. She said more clear public health guidance was needed for use in places like K-12 schools.
A national example
A tsunami of rapid antigen tests is coming, and the Pac-12’s data could help inform their use nationwide.
The federal government in August inked a $760 million contract with Abbott Laboratories for 150 million rapid antigen tests using its platform.
“Production volumes are ramping up really significantly,” said Reed Schuler, a senior adviser to Gov. Jay Inslee.
Meantime, Quidel CEO Douglas Bryant told the San Jose Mercury News it planned to use Pac-12 data to refine its testing algorithms. (Harmon said the conference had yet to sign a research agreement to provide the company data access.)
Harmon and several researchers plan to assess de-identified athlete data for quality control and to produce a study that could help “figure out if that’s a direction we should be going as a country,” she said, adding that the study would be published whether results reflected favorably or poorly on the testing regime.
Washington state health officials are expecting to receive nearly 2.3 million Abbott antigen tests from the federal government by December. Initially, the tests are aimed for community health centers, tribal clinics and some rural hospitals, particularly in areas where testing needs a boost.
For now, state health officials recommend prioritizing use of these tests for people with symptoms.
Using a new type of test also means tracking more testing data.
The state this week began reporting a weekly count of antigen tests separate from its standard COVID-19 data dashboards. Positive antigen test results not confirmed with PCR testing are not currently reflected in those data dashboards.
Tallies of test results help the public understand how prevalent the virus is. But the state Department of Health has struggled to process and publish coronavirus testing data in the past, and the prospect of huge volumes of antigen data presents a new, potentially confounding element.
“It’s kind of the wild West in some ways with these tests,” Schuler said.
Seattle Times sports reporter Mike Vorel contributed to this story.