Are rapid antigen tests the answer for Idaho schools, the Boise State football team?
It can take days — sometimes even weeks — for a patient to learn the results of a polymerase chain reaction (PCR) test for COVID-19.
But there is a new test on the market that can reduce that wait time to a matter of minutes, allowing infected individuals to be immediately identified and quarantined.
In the coming weeks, rapid antigen tests could play a key role in keeping Idaho students in the classroom and the Boise State football team on the field by catching cases before they lead to outbreaks.
Gov. Brad Little recently announced Idaho will receive an additional 530,000 Abbott BinaxNOW rapid antigen tests from the federal government. The inexpensive, simple tests have been earmarked for Idaho schools and were already in use at long-term care facilities statewide.
The United States spent $760 million on 150 million of these tests from health care company Abbott Laboratories in late August to ensure equitable distribution, according to a report from Nature.com.
Meanwhile, the Mountain West’s board of directors voted Sept. 24 to resume the fall football season after forming a partnership with Quest Diagnostics that will allow players, coaches and staff to be tested three times per week. Mountain West Commissioner Craig Thompson said testing will likely cost “in the millions of dollars,” and will be paid for using the league’s reserve funds.
Although antigen tests are faster and cheaper than laboratory PCR tests, they are not as sensitive. There are nearly 100 companies developing or manufacturing rapid tests for SARS-CoV-2 antigen detection, according to the World Health Organization. But only five companies have received U.S. Food and Drug Administration (FDA) Emergency Use Authorization (EUA) — Abbott Diagnostics; LumiraDx UK Ltd.; Becton, Dickinson and Co.; Quidel Corp; and Access Bio Inc. Quest is in the process of obtaining Emergency Use Authorization, a Mountain West spokesperson said.
Antigen testing is just beginning to make its way into the Treasure Valley’s health care systems. Saint Alphonsus conducts antigen testing using a Quidel product, and St. Luke’s is in the process of deciding how it wants to incorporate antigen testing into its protocol. Saltzer Health and Primary Health Medical Group do not currently offer antigen testing.
Idaho considers positives on antigen tests to be probable, not confirmed, COVID-19 cases.
“It’s a fairly recent player to the market,” said Dr. Joshua Kern, a family medicine doctor in Jerome and the vice president of medical affairs for St. Luke’s Magic Valley, Jerome and Wood River, “which is why there’s more and more conversation about it.”
How do antigen tests work?
While the high-sensitivity PCR test requires a laboratory machine, the antigen test is similar in form to an at-home pregnancy test. But instead of urine, antigen tests require a respiratory specimen collected using a “less invasive nasal swab” or, in some cases, saliva.
“It looks a little bit more like a tabletop-type pregnancy test than like something that needs to be run in the lab,” Kern said.
PCR tests detect a virus’s genetic material. Antigen tests target the virus’s nucleocapsid protein and can produce results within 10 to 30 minutes after a specimen is applied to a test strip. A positive test is indicated by a fluorescent glow or as a dark band on the test strip.
The Quidel, LumiraDx and Becton, Dickinson and Co. antigen tests require a specialized, portable reader. Quidel is providing testing to the Pac-12 Conference, and the company claims its antigen test agrees with PCR results 99.5% of the time, according to a study cited in the EUA paperwork that tested 209 symptomatic patients using a direct nasal swab.
If a Boise State football player tests positive using an antigen test, the Mountain West then requires a PCR test to confirm the results. Test results must be completed and recorded prior to each game. The Broncos kick off the 2020 season against Utah State at 5 p.m. Oct. 24 at Albertsons Stadium.
“Rapid antigen testing may be considered for serial testing of individuals who are participating in group events in lower-risk settings (such as outdoor group activities), although data to guide the use of rapid antigen tests as a screening test in asymptomatic individuals are limited,” according to the Idaho Department of Health and Welfare in its guidance for rapid antigen test use, which was updated Sept. 28.
Idaho has already received two shipments of Abbott BinaxNOW tests totaling more than 70,000, according to Health and Welfare, and will receive the remainder of the 530,000 tests in the coming months. The early shipments of Abbott tests will be prioritized for teachers and staff who are symptomatic for COVID-19. Future shipments will be distributed to high-priority populations in addition to schools, Health and Welfare said.
“The new rapid tests are a game changer for schools,” Little said. “The new tests quickly determine who has and does not have COVID-19 so students and teachers can be back in their classrooms.”
Health and Welfare emphasized that the Abbott tests “cannot be used for individuals who do not have symptoms.”
What’s the upside of antigen tests?
The appeal of the antigen test is straightforward — speed and cost.
Results can be delivered in as little as 10 minutes, and the cost ranges from $1 to $5, according to The New York Times.
A spokesperson for the Mountain West said the cost per test is unknown “as the details and protocol with Quest are still being finalized.” The Abbott BinaxNOW rapid antigen test being used in Idaho schools costs $5 per test.
These attributes make the tests appealing to schools and athletic teams because they can potentially identify infectious individuals immediately and remove them from the general population.
“Although more evidence is needed on real-world performance and operational aspects, (antigen tests) are most likely to perform well in patients with high viral loads, which usually appear in the pre-symptomatic (1-3 days before symptom onset) and early symptomatic phases of the illness (within the first 5-7 days of illness),” according to the World Health Organization.
“This offers the opportunity for early diagnosis and interruption of transmission through targeted isolation and cohorting of the most infectious cases and their close contacts.”
Dr. Michael Mina, an assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health, has been an outspoken supporter and leading expert on antigen testing. Mina has been quoted in articles for The New York Times and The Atlantic, among others.
“If you’re at risk of transmitting the virus to somebody else, you’re going to have plenty of viral particles — those would certainly show up in antigen tests,” Mina told Nature.com.
What’s the downside of antigen tests?
According to the U.S. Food and Drug Administration, antigen tests have a higher chance of missing an active coronavirus infection.
For patients who have experienced symptoms for more than five to seven days, the likelihood of a false negative with an antigen test is higher because the individual is more likely to have lower viral loads, according to the World Health Organization.
“Negative results from an antigen test should be considered in the context of clinical observations, patient history and epidemiological information,” said Brett Giroir, assistant secretary for health at the U.S. Department of Health and Human Services, in a news release from HHS.gov.
“Negative antigen tests do not need to be repeated or confirmed with a high-sensitivity molecular test when they are employed for routine screening or surveillance.”
Critics of widespread antigen testing worry they could provide users with a false sense of security.
Just such a scenario played out recently at the Supreme Court nomination ceremony at the White House for Amy Coney Barrett.
The White House has said all guests tested negative for the virus before the event, according to reports from The New York Times and USA Today, but at least eight people who attended the ceremony have since tested positive, including President Donald Trump and first lady Melania Trump.
Many of the guests in attendance did not wear masks and were not appropriately socially distanced.
“It’s a total slice in time that in that moment you’re negative,” said Dr. Lewis Nelson, professor and chair of emergency medicine at Rutgers New Jersey Medical School, in an interview with USA Today. “The moment your test comes back negative, you are no longer negative.”
The first antigen tests that received the FDA’s Emergency Use Authorization had a sensitivity ranging from 84% to 97.6% compared to a standard PCR test, according to the CDC. It’s possible antigen tests could also produce a false negative in a short window early in the infection.
“CDC recommends confirming negative antigen test results with a (PCR) test when the pretest probability is relatively high, especially if the patient is symptomatic or has a known exposure to a person confirmed to have COVID-19,” the CDC said in its guidance for rapid antigen testing.
That’s why Mina and his colleagues recommend frequent screening to circumvent the possibility of a false negative.
“If we had an infinite amount of testing and we could do all the testing we wanted, we would probably be fine with doing a lot more asymptomatic (PCR) testing and testing other groups of people and screening nursing homes,” Kern, of St. Luke’s, said. “There’s a whole state task force that developed a set of guidelines, but the amount of testing that that would create we knew would not be sustainable by the infrastructure available in Idaho.”
The higher cost and less abundant nature of the PCR test paved the way for the antigen test’s more widespread use. Whether these new tests prove helpful or harmful will be an experiment Idahoans can watch in real time.
Health and Welfare posted guidance in August, updated in September, that encouraged caution when using antigen tests to screen participants in contact sports.
“A negative rapid antigen test result should be considered a ‘presumptive negative’ and should never be used as the sole criteria to permit the tested individual to engage in unprotected interaction with others, particularly in high-risk group settings such as congregate living facilities (e.g., long-term care facilities, correctional facilities, etc.), congregate employment settings, contact sports, schools, etc.,” the Health and Welfare guidance said.
Armed with this information from Health and Welfare, Boise State plans to go one step further in its COVID-19 testing than what the Mountain West has prescribed.
“The (Mountain West) has established its own rules for conference-sponsored COVID testing for this season. MW protocols include repetitive rapid antigen testing that takes into account the sensitivity and specificity of the test,” Boise State said in a written statement. “All positive antigen tests will be confirmed by PCR testing per MW protocols.
“The university intends to conduct its own PCR testing on student-athletes, coaching and support staff for all sports in addition to the conference-sponsored testing for football.”
This story was originally published October 15, 2020 at 4:00 AM.
