The U.S. Food and Drug Administration (FDA) has published guidance for diagnostics developers that it said will enable broad diagnostic testing of asymptomatic people and sample pooling during the COVID-19 pandemic.
The template updates provide guidance on validating molecular diagnostics for these purposes and getting them cleared through the agency's emergency use authorization (EUA) pathway.
"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," the FDA explained in a June 16 statement.
Guidance on pooling samples during testing is intended as an aid during the pandemic, as it minimizes use of supplies, which have not been adequate. While mixing samples in a batch reduces the number of tests needed and saves on supplies, there is a greater risk for false-negative results. The technique works best when low prevalence of the coronavirus is expected.
"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 the population is at low risk for contracting COVID-19, developers may be interested in using pooling techniques in tests used for asymptomatic screening," the agency said.
Information in the clinical laboratory test section of frequently asked questions has been updated to clarify the FDA's thinking on testing of asymptomatic people. Most COVID-19 diagnostics that have EUAs from the agency were cleared for individuals with suspected infection. This covers people who are asymptomatic, presymptomatic, and symptomatic, with use guided by a healthcare provider.
Tests need to be specifically authorized by the FDA for broad screening of asymptomatic populations. For this purpose, a highly sensitive test is needed for the most accurate results, and point-of-care tests tend to be less sensitive than laboratory-based tests, according to the agency.
"Although current data suggests that asymptomatic and symptomatic individuals with COVID-19 may have similar levels of viral genetic material in their anterior nares and other upper respiratory sites, there is limited data on the viral loads at different timepoints, in asymptomatic and pre-symptomatic individuals," the FDA advised.
Guidelines on diagnostic testing from the U.S. Centers for Disease Control and Prevention (CDC), which were last updated on June 13, mainly focus on people who are symptomatic or who have had a known exposure to the coronavirus. However, the CDC also has provided guidance on testing asymptomatic people without known exposure in certain settings where the coronavirus is a particular risk and where regular and broad testing of all may be a good idea, including long-term care facilities, and high-density critical infrastructure workplaces where continuity of operations is a high priority.
