Is Abbott Antigen Test Answer to US COVID-19 Testing Problems? Stakeholders Emphasize Caution

NEW YORK – With no signs that the coronavirus pandemic is anywhere close to abating, many have pointed to the need for an easy-to-use, quick, and inexpensive test that could identify those with SARS-COV-2 relatively accurately. 

Last week, Abbott Laboratories appeared to answer that call when its BinaxNow COVID-19 Ag Card antigen test received Emergency Use Authorization from the US Food and Drug Administration, making it the sixth test for the coronavirus in Abbott's portfolio.

But members of the laboratory community stressed cautious expectations for the test, saying they can be used by untrained personnel and may be vulnerable to improper handling, leading to incorrect results.

Protein-based antigen tests have become more popular in recent months as test developers aim to address the ever-increasing demand for COVID-19 tests. The fast turnaround time, ease of use, and ability to ramp up production quickly make them appealing options as outbreaks continue across the US. So far, Quidel, Becton Dickinson, and LumiraDx have received EUA for rapid antigen tests.

Unlike those rapid antigen tests, or molecular COVID-19 tests, the Abbott lateral flow test doesn't require an analyzer to read results. It can tell whether someone has the SARS-COV-2 virus in 15 minutes from a nasal swab that is twirled on a test card with a reagent added, and similar to a pregnancy test, results can be read directly from the card, with one line indicating a negative result and two lines indicating a positive result, according to the FDA. It is authorized for use within seven days of symptoms at CLIA-waived point-of-care settings, including doctors' offices, emergency rooms, and schools, the agency said.

The test is accompanied by a free phone app, Navica, that can display the results and the date of the result when it's requested. Andrea Wainer, executive VP of rapid and molecular diagnostics at Abbott, said during a press briefing that the encrypted results will look like a boarding pass that can be scanned by a verifier to enter a facility.

Abbott announced the test will retail for $5 and it plans to ship "tens of millions" of tests in September, ramping to 50 million tests per month in October, although it is still finalizing distribution plans. The test has a sensitivity of 97 percent and specificity of 98.5 percent, and it qualitatively detects the nucleocapsid protein antigen from SARS-CoV-2. The FDA noted in its EUA that antigen tests may be less sensitive than molecular tests, so a negative result could require a confirmation from a molecular test.

The federal government has shown faith in the test, announcing last week it had purchased 150 million tests to expand evidence-based testing in the US, according to the Department of Health and Human Services. The tests will potentially be deployed to schools and "other special needs populations," the agency said.

Abbott's assay comes as testing shortages have continued throughout the US, due to supply chain issues and high demand. Abbott has positioned the test as a solution to the need for "massive scale testing," Wainer said, adding "We can get to more places and more people and more frequently with a fast result."

The manufacturing ramp-up will be essential to meet continued demand for testing. "For us to be able to control this [pandemic], we need to have results in real time, where patients can hear them and then obviate their behavior based on what they've heard," Frank Peacock, research director for the department of emergency medicine at Baylor College of Medicine, said on Abbott's media call.

John Hackett, Abbott's divisional VP of applied research and technology in the diagnostics business, also noted on the media call that the test can be used "as a first line of defense" to identify people that are currently infected to prevent spread of the virus. He said Abbott designed the test to address multiple critical components of COVID-19 testing, including speed, access, affordability, and accuracy.

Susan Van Meter, the executive director of diagnostics advocacy group AdvaMedDx, emphasized in an email the importance of increasing access to testing, writing that innovations like the Abbott test are "democratizing access to coronavirus tests and ensuring access to results as quickly as possible."

In particular, the low cost of the test will help with accessibility, because "affordability is critical to get our tests out to as many people as we can," Wainer added. She said Abbott chose to use antigen technology because it would be able to get to a more affordable price point, and the $5 kit includes the card, the swab, and the buffer.

But despite the solid performance data and ease of use, some members of the laboratory community have their doubts about how significant the impact of the test will be. Emily Volk, president-elect of the College of American Pathologists, noted that Abbott will have to make sure the end users know exactly how to use the test and interpret the results.

She mentioned that variables, such as improper collection of a sample, not applying the sample to the card properly, or not running and interpreting the results within the appropriate time limits could lead to inaccurate results. Volk also emphasized that there is less direct oversight at the point of care than in a centralized laboratory, which could impact proper use of the test. "That's a lot of ifs, and we don't live in a world that's that controlled," Volk said.

She did add that the rapid turnaround time could help expand availability, as long as Abbott is able to produce enough tests. The supply chain issues that have compromised the US response to the pandemic shouldn't be a problem for this test, Volk said, since it uses a different supply chain than molecular tests.

"I think it's very possible this will have some impact, but I don't see this revolutionizing or significantly decreasing the need for PCR tests in commercial laboratories," Volk said. "I do not see it as being a substitute for PCR tests in the acute care setting." 

Alex Greninger, the assistant director of the University of Washington Medicine Clinical Virology Laboratory and an assistant professor of laboratory medicine at the university, noted in an email the limited performance data in the EUA and said the most important aspect is that it was only evaluated for symptomatic patients, which he called "a moderately different use case than something manufactured at" 1 million to 1.5 million a day, He added that it would be interesting to see how the specificity of the test holds up if it is run at that volume. 

The lack of a required instrument makes Abbott's test stand out from the rest in terms of access, since the other antigen tests that have received EUA each require instrumentation.

While rapid antigen tests have shown to be less accurate than molecular tests, in general, some have advocated for their use during the pandemic in order to ramp up testing, saying the lower sensitivity of antigen tests is made up for by their ease of use and potential to get more people tested.

According to Michael Mina, an assistant professor of epidemiology at Harvard's T.H. Chan School of Public Health, because the rapid antigen tests are reserved for use within a week of symptoms, the positive result comes when patients are often still transmitting the virus. During the recent spike in coronavirus cases during the summer, some commercial labs took up to two weeks to report COVID-19 molecular test results. Such a delay could lead to a positive result for a patient who is no longer contagious, resulting in erroneous quarantines. "People actually test positive for much longer on PCR than they do on antigen tests," Mina said on a call with reporters. 

Mina also said he thinks Abbott's test, and other rapid antigen tests that may follow, could be used for asymptomatic patients and over-the-counter use. "I think having a test that can really find you when you're transmissible is the whole goal here," Mina said. When results are quick, the transmission chain can be stopped and outbreaks can be avoided, he added, and as COVID-19 tests go over-the-counter, there will need to be flexibility in how results are reported, since many patients could be testing from home.

"The test could have an impact," Volk said. "It really depends on who gets them and how they get them and in what quantity."