On July 18, 2020, the U.S. Food and Drug Administration (FDA) issued an emergency use authorization (EUA) for sample pooling of specimens when using the SARS-CoV-2 rRT-PCR diagnostic test from Quest Diagnostics. This EUA permits testing up to four samples together in a batch with a single diagnostic test, also known as sample pooling, which increases efficiency, given that the majority of COVID-19 test samples return negative results. This move comes on the heels of FDA’s June 16 guidance for COVID-19 test developers interested in using pooled samples to preserve test resources and increase efficiency. It is the first test for which FDA has granted an EUA to utilize this technique, and will likely lead to authorization of other tests for similar purposes.
According to FDA, this EUA and the ability to perform sample pooling is part of government efforts to ensure that larger numbers of COVID-19 tests are performed more quickly and to conserve test supplies. Increasing testing for COVID-19 is crucial for ongoing surveillance and detection of the disease. Pooled samples that return negative results for presence of the virus likely mean all the patients tested were negative for COVID-19. However, if there is a positive result, then each of the samples pooled must be tested individually to identify the positive sample(s). In areas with low prevalence of COVID-19 where fewer positive results are expected, sample pooling can assist with surveillance and broad testing in a manner that may be quicker and more cost-efficient.
Key Takeaways
FDA’s actions in issuing this EUA demonstrate the desire for continued expansion of COVID-19 testing as various geographic locales detect and manage infections. Stakeholders involved in developing COVID-19 tests, testing patients and processing test samples should carefully review the EUA, as there may be implications for laboratories, healthcare providers and others. There may also be some risks in using this technique as there is a greater likelihood of false negative results if not properly validated.
Laboratory developers of COVID-19 tests seeking to expedite testing by pooling samples should ensure that they obtain an EUA from FDA for use with their test, according to FDA’s guidance. Likewise, laboratories interested in pooling samples should ensure that they use COVID-19 tests authorized by FDA for sample pooling. Additionally, laboratories may consider focusing efforts to use sample pooling in geographic areas that are not experiencing COVID-19 surges, since hot spots would likely have greater numbers of positive cases and could necessitate more retesting of individual samples. In addition, hospitals, test sites and other essential businesses that may need to test significant numbers of individuals should be aware that certain samples sent to laboratories might be pooled.
Finally, employers and others looking to test on a larger scale as areas of the country reopen may want to consider pooling samples as a way to screen employees or large groups for COVID-19 more efficiently. However, these entities should also remain aware that sample pooling may heighten the risk of false negatives because of sample dilution. Consequently, where an individual has a low viral count, the dilution of the individual’s sample when combined with other samples could result in the testing mechanism being unable to detect the presence of the virus and lead to a false negative result. Entities using sample pooling may consider more frequent testing or other methods to mitigate this risk.
Keeping up with the high demand of COVID-19 testing has proven a challenge for healthcare centers around the world. Pooled testing may have a significant impact in reducing testing time, supply usage and resource allocation.
