As concerns about the accuracy of some of the antibody tests on the market continue to rise, will the FDA be updating their policy/guidance on the evaluation of antibody tests?
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. We have moved quickly and thoughtfully, recognizing the distinct, yet equally important roles that diagnostic tests and antibody tests can play in our nation’s response. Our March 16th policy for serological tests is intended to provide flexibility to laboratories and point-of-care settings to begin testing as long as those tests were properly validated and labeled as outlined in our policy. (Under the Clinical Laboratory Improvements Act (CLIA), serology tests can only be used in labs certified for high-complexity testing, including through point-of-care settings covered by a high-complexity laboratory’s CLIA certificate, unless the tests are otherwise categorized by FDA, for example, through an EUA. This is another mitigating step to help to ensure only validated tests are used in the U.S. population.) The March 16th guidance outlined a policy appropriate for antibody tests that are not meant to diagnose SARS-CoV-2 infection because the policy helped expand access to testing so that researchers could begin to understand critical questions about the prevalence of COVID-19 infections in different communities, as well as assess whether the presence of antibodies conveys immunity, and if so, for how long, which is important information to inform the use of serology tests in the future. As we have stated, we will continue to consider the risks and benefits of our policies as the public health emergency evolves and adjust as necessary.
What is most important for our viewers to understand about antibody testing at this time?
An antibody test is not designed to diagnose an active COVID-19 infection (specifically from the SARS-CoV-2 virus). These tests are intended for use as an aid in identifying individuals with an adaptive immune response to the SARS-CoV-2 virus, either as part of an active infection or a prior infection. The tests detect the presence of antibodies in the blood – if antibodies are present, that indicates that the person has been exposed to the virus and developed antibodies against it, which may mean that person has at least some immunity to the coronavirus. In the early days of an infection when the body’s immune response is still building, antibodies may not be detected, which is why serological tests alone should not be used to diagnose or exclude infection with the SARS-CoV-2 virus.
There is still a great deal about COVID-19 immunity that we don’t yet fully understand. For example, we don’t yet know that just because someone has developed antibodies, that they are fully protected from reinfection, or how long any immunity lasts. We do expect that data from more widespread serological testing will help us track the spread of the virus nationwide and assess the impact of our public health efforts now, while also informing our COVID-19 response as we continue to move forward. Determining the next steps in our response to COVID-19 is partially dependent on an accurate assessment of our national efforts thus far, and the quality of data for making this decision is dependent on accurate testing products.