COVID molecules and face mask Theinclusion of antibody testing could provide a more accurate meansof figuring out how many people have been infected. (Image:Shutterstock)

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Aspen was an early COVID-19 hot spot in Colorado, with a clusterof cases in March linked to tourists visiting for its world-famousskiing. Tests were in short supply, making it difficult to know howthe virus was spreading.

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So in April, when the Pitkin County Public Health Departmentannounced it had obtained 1,000 COVID-19 antibody tests that itwould offer residents at no charge, it seemed like an excitingopportunity to evaluate the efforts underway to stop the spread ofthe virus.

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Related: COVID-19 return to work testing: guidance forbrokers and employers

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"This test will allow us to get the epidemiological data thatwe've been looking for," AspenAmbulance District director Gabe Muething said during an April9 community meeting held online.

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However, the plan soon fell apart amid questions about thereliability of the test from Aytu BioScience. Other ski towns suchas Telluride, Colorado, and Jackson, Wyoming, as well as the lesswealthy border community of Laredo, Texas, were also drawn toantibody testing to inform decisions about how to exit lockdown.But they, too, determined the tests weren't living up to theirpromise.

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The allure of antibody tests is understandable. Although theycan't find active cases of COVID-19, they can identify people whopreviously have been infected with the coronavirus that causes thedisease, which could give health officials importantepidemiological information about how widely it has spread in acommunity and the extent of asymptomatic cases. In theory, atleast, antibodies would be present in such people whether they hada severe case, little more than a dry cough or no complaints atall.

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Even more enticing: These tests were billed as a path to restartlocal economies by identifying people who might be immune to thevirus and could therefore safely return to the public sphere.

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But, in these and other communities, testing programs initiallyslated to test hundreds or thousands have been scaled back or puton hold.

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"I don't think these tests are ready for clinical use yet," saidUniversity of California-San Francisco immunologist Dr. Alexander Marson,who has studied their reliability. He and his team vetted 12different antibody tests and found all but one turned up falsepositives — implying that someone had antibodies when they didn't ―with false-positive rates reaching as high as 16%. (Thestudy is preliminary and has not been peer-reviewedyet.)

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More than 100 antibody tests are currently available in theU.S., including offerings by commercial labs, academic centers andsmall entrepreneurial ventures. As serious questions emergedearlier this month about the accuracy of the tests and theusefulness of the results, the U.S. Food and Drug Administrationsaid it will require companies to submit validation data on their productsand apply for emergency-useauthorizations for their products. (Previously, companies wereallowed to sell their tests without review from the FDA, as long asthey did their own validation and included a disclaimer.) And theAmerican Medical Association said on May 14 that the tests should not be used to assess an individual's immunity orwhen to end physical distancing.

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And this week, the Centers for Disease Control and Preventionreleased newguidelines warning that antibody test results can havehigh false positive rates and should not be used to make decisionsabout returning people to work, schools, dorms or other placeswhere people congregate.

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Once hailed as a solution, the current crop of tests, which havenot been thoroughly vetted by any regulatory agency, now seem morelikely to add chaos and uncertainty to a situation already fraughtwith anxiety. "To give people a false sense of security has a lotof danger right now," said Dr. TravisRiddell, the health officer for Teton County, which includesJackson, Wyoming.

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Accuracy questions raised

The gold standard for confirming an active COVID-19 infection isto take a swab from the nasopharynx and test it for the presence ofviral RNA. The antibody tests instead parse the blood forantibodies against the COVID-19 virus. It takes time for aninfected person to produce antibodies, so these tests can'tdiagnose an ongoing infection, only indicate that a person hasencountered the virus.

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In Aspen, county officials knew the FDA had not approved theAytu BioScience test, which the Colorado-based company wasimporting from China. So they first conducted their own validationtests, said Bill Linn, spokesperson for the Pitkin County IncidentManagement Team. "We weren't reassured enough by our own testing tofeel like we should move ahead."

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In Laredo, officials had been told by one of the communitymembers helping to arrange the purchase of 20,000 tests from the Chinese company Anhui DeepBlue MedicalTechnology that they were FDA-approved, but the city's ownvalidation trials revealed only about a 20% accuracy rate, saidLaredo spokesperson Rafael Benavides. Before Laredo could pay forthe tests, Benavides said, an arm of U.S. Immigration and CustomsEnforcement seized them and launched an investigation.

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Neither Anhui DeepBlue Medical Technology, nor Aytu returnedrequests for comment.

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In March, Covaxx, a company led by two part-time Tellurideresidents, offered to test residents of the town and thesurrounding county with an antibody test it had developed. But the project was suspendedindefinitely when the company's testing facility fell behind onprocessing them.

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The county is committed to doing a second round of testing butis evaluating how to proceed, said San Miguel County spokespersonSusan Lilly. "The question is how do you target it to be the mostrelevant clinically and for the public health team'sdecision-making moving forward?"

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Officials back off, community members stepin

On May 4, the FDA updated its antibody test policy to require that manufacturerssubmit validation data, but it is still allowing the tests to besold without the normallengthy vetting and approval process, whichincludes demonstratingsafety and effectiveness.

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In some wealthy areas, government officials had been offeringfree tests from startups with local investors. In Jackson, forexample, a venture capitalist with an investment in Covaxx, thetest used in Telluride, offered to help the city obtain 1,000tests. But after reviewing the offer, Teton County declined overconcerns about the test's accuracy. "If a person tests positive,what does that mean? And is that useful information? We just don'tknow yet," Riddell said.

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Covaxx spokesperson John Schaefer said in a statement that thetest had been validated on more than 900 blood samples and is beingreviewed by the FDA.

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After Teton County officials decided against community antibodytesting, a private nonprofit, Test Teton Now, sprung up to providefree COVID-19 antibody testing using the Covaxx test for roughly8,000 people, about a third of the county's residents. As of May22, they'd raised $396,000 and tested 843 samples. The group has"done a lot" to verify the Covaxx tests, said Test Teton Nowpresident Shaun Andrikopoulos. "I don't want to call it validation,because we didn't go through an independent review board, but wehave sent our samples out to other labs."

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Organizers of Test Teton Now don't share others' concerns aboutthe test's utility. "We don't encourage people to make anydecisions about what they're going to do or how they're going tobehave based on the results," said the nonprofit's spokesperson,Jennifer Ford.

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What good is a test that can't be used for practical purposes?"We think knowledge is power, and data is the beginning ofknowledge," Ford said. But unreliable data doesn't give knowledge,it gives an illusion of knowledge.

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So many unknowns remain, and false data may be worse than none.Even a very accurate test will produce a large number of falsepositives when used in a population where few people have beeninfected. If only 4% of people have actually been infected, a testwith 95% accuracy would produce nine positive results for every 100tests, five of which are false positives.

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And that creates a danger that the tests could lead people toincorrectly think that they have antibodies that make them immune,which could have disastrous consequences if they changed theirbehavior as a result. Consider, for example, a person falsely toldshe had antibodies going to work at a nursing home, believing shecouldn't catch or spread the virus to anyone.

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It's not even known for sure that having antibodies makessomeone immune. Researchers are hopeful that exposure can confersome level of immunity, but how strong that immunity might be andhow long it might last remain unknown, said Harvard epidemiologistMarcLipsitch.

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So, having been burned once, Aspen has put antibody testing onhold and is instead focusing on identifying and isolating peoplewho are sick or at risk of becoming so. "It's actually a step backto where we started," Linn said.

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Given the remaining unknowns about immunity and COVID-19, thebest methods for addressing the pandemic in communities may be themost time-tested ones, Linn said. "Put the sick people in placeswhere they can't get anyone else sick. It's the bread and butter ofepidemiology."

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Kaiser HealthNews (KHN) is a national health policy news service. It is aneditorially independent program of the Henry J. Kaiser Family Foundation whichis not affiliated with Kaiser Permanente.

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