Tests designed to identify people with covid-19 antibodies, but which sometimes yield negative results even in infected patients, have been falsely advertised by some test makers as effective in the screening of potential covid-19 patients.
Food and Drug Administration (FDA) Commissioner Stephen Hahn said in a statement Saturday that not only have some test developers falsely claimed that antibody tests can be used to diagnose covid-19, they have erroneously declared the tests approved by the Food and Drug Administration.
“We have also updated our website to better clarify which tests have been authorised by FDA and which have not been authorised,” Hahn said. “However, some test developers have misused the serology test kit notification list to falsely claim their serological tests are FDA approved or authorised. Others have falsely claimed that their tests can diagnose COVID-19.”
Hahn previously warned of deceptive claims by some test developers on April 7. White House coronavirus task force coordinator Deborah Birx also drew attention to the online sales of unreliable tests this month, saying they risked giving people “false reassurance.”
Antibody tests—also known as serological tests—allow healthcare professionals to identify people who’ve been exposed to the novel coronavirus after they’ve developed an immune response. They differ from diagnostic tests in that they’re able to identify not only people with active infections, but those who’ve recovered as well.
But antibody tests are not reliable for ruling out the presence of the coronavirus. To wit, a person may be infected with the virus and transmit it to others for several days before antibodies form.
“Every step we have taken as part of our approach to COVID-19 testing has been a careful balancing of risks and benefits in order to meet the urgent public health needs as we combat this new pathogen,” said Hahn. “We have moved quickly and thoughtfully, and we are continuing to learn and adapt based on the real-world experience and data we’re seeing.”
The FDA, in an effort to accelerate testing in March, issued a policy relaxing rules around the development and use of antibody tests. The FDA said it would not intervene if companies sold the tests without FDA approval provided the developer certified them as accurate and reliable, provided notification to the FDA, and labelled the tests with a note that they are inadequate alone for diagnosis.
As opposed to the molecular diagnostic tests used by hospitals and laboratories to confirm whether a patient is covid-19 positive, serological tests could prove useful in determining which a person is less susceptible to infection. What’s more, researchers are investigating whether convalescent plasma—the liquid part of blood that contains antibodies from a person recovered from a disease—might serve as treatment in seriously covid-19 case.
At present, these applications remain purely hypothetical. Scientists have yet to determine whether a person with covid-19 antibodies is protected from reinfection; if they are, it’s unclear long that immunity lasts.
“These are questions that we still have scientifically,” Dr. Birx said Sunday on CBS News’ Face the Nation. “In most infectious diseases, except for HIV, we know that when you get sick and you recover and you develop an antibody, that that antibody often confers immunity. We just don’t know if it’s immunity for a month, immunity for six months, immunity for six years.”
Several states have announced initiatives that aim to determine whether antibody measurements can serve as an indicator of immunity. Kentucky healthcare workers exposed to the coronavirus, for example, are donating plasma as part of the state’s Co-Immunity Project. Two critically-ill patients in Georgia were given plasma from recovered patients last week. Hinh said on Saturday that the FDA had granted four emergency-use authorizations for serological tests so far and expects that number to rise in coming weeks.
At time of writing, the U.S. had confirmed nearly 762,000 cases of the virus, which has ravaged global markets and killed more than 167,000 worldwide.