Antibody or serology tests are designed to identify people who may have overcome covid-19, including those who have had no symptoms and who have developed an immune response. They are not designed to detect active infections. Some officials tout blood tests as a way to reopen the economy by identifying people who have developed immunity and can return to work safely. But many scientists, as well as the World Health Organization, say that even high-quality antibody tests can prove that a person is immune to the new coronavirus and is not at risk of being re-infected.
Now, the emergence of dozens of tests never reviewed by the FDA – many of which are aggressively marketed – could confuse the doctors, hospitals, employers and consumers who claim the products, according to critics who say supervision by the testing agency was lax. The issues are of particular importance as federal and state officials debate various strategies, including the use of serological tests, to help determine when they can end local and state lockouts.
“A test is only as good as its results,” said Kelly Wroblewski, director of infectious disease programs at the Association of Public Health Labs, who urged the FDA to take a closer look at unapproved tests. “Having many inaccurate tests is worse than not having any at all.”
Fueled by such concerns, the FDA recently stepped up the warnings and joined other agencies, including the National Cancer Institute, to try to determine whether uncontrolled tests actually work.
Thursday in an interview with the Washington Post Live, FDA Commissioner Stephen Hahn said “people should be very careful” about tests that have not gone through the rigorous process of obtaining an authorization for emergency use by the agency. So far, only four tests have received these approvals: Cellex, Chembio Diagnostic Systems, Ortho Clinical Diagnostics and Mount Sinai Laboratory.
Much of the validation work for unauthorized testing will be done by NCI, in collaboration with the Centers for Disease Control and Prevention, the National Institute of Allergies and Infectious Diseases, and university labs. The cancer institute will use its human papillomavirus (HPV) serology lab at the Frederick National Laboratory for work. Assessments will also be carried out for certain tests to obtain emergency clearance from the FDA, Hahn said in a statement on Saturday evening. The goal is to have “more confidence in test performance,” he said.
Meanwhile, however, the unrevised tests remain on the market. In mid-March, the FDA, wanting to guarantee rapid access to serological tests, said that manufacturers could sell them after validating the results themselves and simply notifying the agency. Product labels must indicate that they are not FDA approved or intended to be used as the sole basis for diagnosing active infections. The agency lists on its website the companies and laboratories that have submitted these notifications. In response to concerns that the list could be viewed as an approval, the agency has updated its website to make it clear which tests are approved by the FDA and which are not, Hahn said.
Test experts warn that the risk of inaccurate testing is high. A bad result could, for example, indicate that individuals are immune to the virus when they do not, which could lead to behavior that endangers themselves and their families. The danger of buying unverified tests has been underscored by the British government’s recent $ 20 million purchase of antibody tests in China that have not worked. Even for high-quality tests, scientists say they do not know the level of antibodies needed to immunize a person against the virus or the duration of protection.
Many of the unrevised tests sold in the United States are manufactured in China or elsewhere in Asia. Distributors strongly advocate for their products as a way to expedite testing in a country facing shortages and to provide individuals, employers and governments with essential information.
Jonathan Cohen, President and CEO of 20/20 GeneSystems, based in Rockville, Md., Said that the test he sells to healthcare professionals and clinical laboratories, named “CoronaCheck”, has been approved by the Chinese equivalent of the FDA and verified by hospitals in the United States. “These tests are pretty good,” he said.
Paul Kahlert, owner and president of ARCpoint Labs in Edina, Minnesota, said customers were anxious to know if they were infected and also if they could donate blood that could be used to make “convalescent plasma” “, Which is under trial. as a potential treatment for people with covid-19. “People are so thankful that we do it,” he said. “They want to help. “
But a fact sheet about ARCpoint antibody tests raises concerns, said Scott Becker, executive director of the Association of Public Health Laboratories. The sheet indicates that the presence of certain antibodies suggests that a person has “functional immunity” and may “interrupt social distancing.” Becker said scientists don’t know enough to say this about antibody testing for the coronavirus.
Amanda Harley, spokesperson for ARCpoint Labs, a franchise company based in Greenville, S.C., said the fact sheet was created as a guide for franchisees and is no longer used. John Constantine, president and chief executive officer of the company, said the company also provides warnings on its product, such that test results are not a guarantee of immunity. “We would never say,” You are good. Go see grandmother without a mask, ”he said.
Antibody tests are generally available in rapid versions that use a small amount of blood from a finger prick and can cost as little as $ 20 or less, or others that rely on traditional blood samples and are considerably more expensive. Many of the finger prickers are marketed for use in doctors’ offices and pharmacies, although the government requires that all unauthorized testing be done in so-called CLIA laboratories certified to perform high complexity tests, said Becker.
The requirement slows the use of antibody tests, say suppliers who argue that doctors should be able to perform point-of-care tests in their offices without using sophisticated laboratories.
Some state and local health departments have also warned consumers and doctors to avoid unauthorized testing. Authorities in San Diego County have shut down an antibody test site at a local community college, citing a lack of documentation for the test.
Some of the unrevised tests have been developed by high quality academic medical centers and are not of concern among public health experts. Emory University, for example, has created a test it plans to use for staff and patients to see how well the virus has been transmitted in their community.
Marybeth Sexton, an infectious disease specialist at Emory, recently got tested because she was wondering if an episode of illness in February was caused by the coronavirus. The test has detected antibodies to the virus, but since she still doesn’t know if she is immune, she plans to continue practicing social distancing and wearing a mask. “I will do nothing different,” she said.
In New York, periodontist Scott Froum said he plans to offer staff and patient antibody tests when it reopens for routine care as an additional layer of protection against the virus. But it struggles with regulations and choices. “You have to be careful,” he said. “Some of the tests don’t look kosher. “
The accuracy of one of the tests is a big problem. Accuracy is usually determined by two measurements, called sensitivity and specificity. The sensitivity of a test is the true positive rate, and a test with a high sensitivity will have few false negatives. The specificity test is the true negative rate, and a test with high specificity will have few false positives.
But even for a very precise test, its predictive value depends on the prevalence of the disease it is intended to detect in the population. Suppose a test is 95% sensitive and 95% specific – a fairly accurate test. But if only 1% of the population were infected, the test would identify many more false positives than true positives. This is because when there are very few people in the population with the disease, the false positives may outnumber the true positives.
A positive result would have a slim chance of being accurate. But if 5% of the population were infected, a positive result would have a 50 to 50 chance of being truly positive.
The FDA is expected to authorize further testing in the coming days and weeks. But to get the volume of serological tests the country needs, officials say, more large manufacturers and laboratories will need to get involved. A major manufacturer, Abbott, recently launched a serological test and plans to produce 20 million tests per month by June. The company said it would apply to the FDA for official approval.
Carolyn Y. Johnson contributed to this report.