COVID-19 Antigen Test Confusion Highlights Need For Better Federal Guidance For SNFs, Experts Say

October 12, 2020, Maggie Flynn, Skilled Nursing News - One state’s ban on the use of point-of-care tests for COVID-19 in skilled nursing facilities has been withdrawn after sharp criticism from the assistant secretary of the Department of Health and Human Services (HHS).  But the incident highlights the confusion around the use of the tests – and the need for clearer federal guidance on how SNFs should use the results to inform decision-making, experts said.

“There wasn’t clear, evidence-based guidance on how to use the tests, and so that basically has left nursing homes and states and counties and everyone scrambling to try to figure it out,” Dr. Michael Wasserman, president of the California Association of Long-Term Care Medicine, told Skilled Nursing News on October 12. 

The main question for nursing homes is not so much how to run the tests, but how to make decisions based on those test results, he explained.

Morgan Katz, an assistant professor of medicine at Johns Hopkins University School of Medicine, agreed.  She was one of the authors of a JAMA Internal Medicine Research letter on the outcomes of universal COVID-19 facility testing.

For screening asymptomatic staff members, the testing initiative has not lived up to the early data that suggested this might be a possibility with these kinds of tests she told SNN.

“I think the best way to use these tests – and I think facilities should start, because there’s been so much confusion – is to use it as a rapid screening for residents that develop any type of symptoms,” she explained.  “Moving into flu season, we’re going to start seeing more and more respiratory issues.  They’re not going to know if it’s COVID, flu, [or] if it’s just a normal cold.”

The state of Nevada on October 9 withdrew a directive issued on October 2 that banned the use of antigen testing in SNFs after HHS assistant secretary for health Adm. Brett Giroir sharply criticized the ban and ordered the state to rescind it.  The ban would have kept SNFs from using the BD Veritor or Quidel Sofia point-of-care antigen tests and supplies, which HHS shipped to SNFs across the U.S. starting in July and through September.

When it was announced in July, the testing push was greeted with both optimism and questions.  While operators and other stakeholders welcomed the help securing testing – especially as the Centers for Medicare & Medicaid Services (CMS) would later issue stricter COVID-19 testing requirements for SNFs – some doubted the accuracy of the antigen tests.

Questions continued to trickle in over August and September, with initial concerns relating to the reliability of the antigen tests for asymptomatic individuals, followed by a report of BD investigating false positives from its tests in nursing homes.

HHS, for its part, acknowledged from the start of the initiative that the point-of-care antigen tests, which detect fragments of proteins on or within the virus, are not as accurate as polymerase chain reaction (PCR) COVID-19 tests, though initial concerns were more centered on false negatives.

Giroir emphasized in September, and again during a call with reporters on October 9, that the rate of false positives for a given diagnostic test will depend on the population spread of the disease that test is designed to detect.

Dr. Christian Bergman, an assistant professor at Virginia Commonwealth University who has worked with AMDA – The Society for Post-Acute and Long-Term Care Medicine on antigen testing, noted that AMDA’s original position on the use of antigen tests called for more clarity on their potential limitations.

“Our original position was that we need more large-scale data in regards to how to respond to a positive antigen test in a person who otherwise has a low, very low pretest probability,” Bergman told SNN on October 12.  “That’s not been clear from a federal standpoint.”

There are essentially three different populations to consider for the tests, Bergman explained:

  • Symptomatic staff and residents
  • Asymptomatic residents
  • Asymptomatic staff, vendors and other health care workers.

All of these populations raise different questions.  Residents and staff with symptoms have “a moderate to high pretest probability that they could have the disease,” and an antigen test would allow for positive patients to be rapidly isolated, or if they are staff, sent home.

But the asymptomatic residents and asymptomatic staff raise very different concerns.

“If you were to use an antigen test as part of let’s say, a facility outbreak investigation, or you’re in the middle of an outbreak, and you’re in the process of doing repeated testing of residents and staff, be very careful about how you interpret an antigen positive test in a resident who otherwise shows no symptoms,” Bergman cautioned.  “Ethically, you would not be able to cohort that person with known PCR positive COVID-19 patients, because that could potentially expose them.”

AMDA has suggested isolating those residents in place and confirming their positive with a PCR test that provides results in 24 or 48 hours, he said.

For staff, it’s easier to ethically isolate them until that confirmatory PCR test arrives, though as Wasserman pointed out, it can put already-short-staffed SNFs in an unpleasant bind.

The Centers for Disease Control and Prevention (CDC) has put out a one-page flowchart of “considerations for interpreting antigen test results in nursing homes,” which HHS attached to its October 8 letter to Nevada telling the state to rescind the ban.

For Bergman, however, this is not sufficient guidance.

“These algorithms have not been clearly defined,” he told SNN.  “The CDC one-page algorithm just deals with everybody as a whole, which is not the right approach.  There are people that have a higher likelihood of having the disease and people that have a lower likelihood of having the disease.”

Many of the SNFs Katz has worked with, in both her consultant capacity and her work with Johns Hopkins, are simply avoiding the antigen tests because of the confusion around how to make use of the results, she told SNN.  She would like to see the federal government provide some scenarios for using the antigen tests, such as the right populations to use the tests on, she told SNN.

Wasserman, Katz and Bergman were all unified on this point: The federal government needs to provide clearer guidance on how nursing homes should act based on antigen test results.

“It’s like throwing mud at the wall,” Wasserman said.  “They sent these tests out to all the nursing homes, so that they could say they have done something. …  I do think these tests have value, [but] they have to be used properly.  I think the federal response to Nevada, of spanking them after giving them tests without great guidance and evidence, is not productive.”