The U.S. FDA detailed which kinds of SARS-CoV-2 tests are getting top priority, with access to rolling, rapid reviews for emergency use authorization (EUA) during the unfolding pandemic. The agency is aiming to authorize point-of-care and at-home tests to better distribute the use of testing in various locations. It also is looking at automated and high-throughput tests that can offer analysis of larger batches of tests at one time.
In addition, the FDA took the time during its June 17 virtual town hall on SARS-CoV-2 to talk through its views on test development for screening asymptomatic individuals, as well as issues around pooling individual screening samples for testing together.
POC and home
“We're very interested in authorizing [both] point-of-care … and home-use tests. With the home-use tests, there are other health care situations where that would also apply,” said Tim Stenzel, director of the Office of In Vitro Diagnostics and Radiological Health at the FDA. “It could be schools, employment, shopping centers; they all fit in the home bucket because a health care worker, potentially based on the authorization, may not be directly involved.
“There [are] so many developers interested in having a point-of-care claim. What I have directed the office to do is that if there is data to review, whether it's complete, or it's on a rolling basis ... that we make data review of point-of-care tests a priority,” he continued.
Stenzel then highlighted the other high-priority bucket, namely tests that are automated and high throughput. “That should be relatively straightforward to explain; those testing platforms that can generate a lot of results in the short amount of time allows us to expand the capability.”
The FDA indicated that it is being inundated with EUA applications for COVID-19 diagnostics, and it is working to prioritize response and interaction with those developers in the most needed categories. However, the relative completeness of the application remains another factor in what gets reviewed. Developers may distribute tests ahead of a complete EUA submission and review, but those are expected to be conducted in a timely manner.
The agency has issued 140 EUAs to date for diagnostic tests for COVID-19. That includes 118 molecular diagnostic tests to identify patients with an infection, 21 serology antibody tests to detect if the patient has had COVID-19 and one antigen test, a category that is expected to complement molecular tests and offer high specificity.
On tests seeking a home-use indication, the lack of a straightforward way to collect data systematically on positive or negative test results remains a difficulty that the agency is working to overcome. Health care providers are obligated to report the results from the tests they use to support population health analytics and measures.
“The ask in this emergency is that positive and negative results get reported,” said Stenzel. “[W]e are open to various ways of doing that and with developers on how that gets accomplished.”
Asymptomatic COVID-19 screening tests and how to conduct pooled data analyses including asymptomatic individuals were also subjects highlighted by the agency during the town hall, as well as in a June 16 letter issued by Jeff Shuren, the director of the Center for Devices and Radiological Health.
Existing molecular tests can be used on asymptomatic individuals who have been exposed to or are suspected of having COVID-19. But the agency has specific requirements for tests for asymptomatic people that are intended to be used to conduct a systematic population analysis.
The Shuren letter highlighted that the FDA has posted template updates to guide the validation of molecular diagnostic tests that are intended to be used for pooling patient samples or for screening asymptomatic individuals not suspected of having COVID-19.
“Today, the FDA outlined the steps for a test to be authorized for broad screening of asymptomatic individuals by publicly providing information in updated templates for test developers on the [agency’s] expectations for how a test can be validated for screening of asymptomatic individuals,” Shuren wrote. “This will make it easier for developers to get their tests authorized for this use. The FDA recognizes that organizations may want to conduct screening of asymptomatic individuals as part of a broader strategy to help ensure the safety of their employees, patients, students and others.”
In screening testing, one approach is to pool samples from several individuals in a single test to reduce the consumption of required resources, such as reagents. If the pooled sample comes back positive, only then are individual samples tested. However, this pooling process can dilute each sample, the agency concluded, thereby boosting the prospect of false negative results.
“This method works well when there is a low prevalence of cases, meaning more negative results are expected,” Shuren’s letter concluded. “Given that testing asymptomatic individuals means testing a greater volume of patients, and a low prevalence may be more likely in an asymptomatic population, particularly if [it] is at low risk for contracting COVID-19, developers may be interested in using pooling techniques in tests used for asymptomatic screening.”
Finally, the FDA noted during the virtual town hall that it had revoked the EUA for Chembio Diagnostic Systems Inc.’s SARS-CoV-2 antibody test, known as the DPP COVID-19 IgM/IgG System, due to performance concerns with test accuracy.
“As we have worked with serology developers in this pandemic, we have gained additional knowledge,” said Stenzel. “We have raised the bar on expectation for serology performance, and Chembio unfortunately was no longer able to meet that bar on subsequent evaluation. So, we have moved to revoke [the] authorization. With all the tests that have been removed from the notification list, the majority, of course, are serology tests.”