Quest Test Gets First FDA Green Light for Sample Pooling to Detect SARS-CoV-2
Things sure happen fast during a pandemic. While the U.S. Food and Drug Administration (FDA) has historically “encourage all test developers to reach out to [us] to discuss appropriate validation approaches,” the agency has remained largely silent on the practice of sample pooling allowing for the testing of multiple individuals with a single test. But […]
Things sure happen fast during a pandemic. While the U.S. Food and Drug Administration (FDA) has historically “encourage all test developers to reach out to [us] to discuss appropriate validation approaches,” the agency has remained largely silent on the practice of sample pooling allowing for the testing of multiple individuals with a single test. But that all changed on June 16 when the agency issued new guidance outlining its “validation expectations” for use of specimen pooling either to develop a new test for Emergency Use Authorization (EUA) or expand the use of a current EUA product. And barely one month later, the FDA pushed the button on the latter by extending the EUA of an existing test to allow for pool sampling to detect the coronavirus.
The Quest SARS-CoV-2 Test
On July 18, the announcement came that Quest Diagnostics’ SARS-CoV-2 RNA test had become the first coronavirus test cleared by the FDA for pooled sampling. Technically, the approval is a reissued version of the existing EUA issued back in March expanded to allow for use of the test with pooled upper respiratory specimens in sample pools comprised of four individuals.
Pooling and the COVID-19 Diagnostic Challenge
Pooling involves mixing sub-samples extracted from individual samples into a pool or “batch” that can be tested with a single test. If the entire pool tests negative, all of the constituent samples are also deemed negative; but if the pool tests positive, the individual samples must be retested to identify the source(s) of the positive.
Use of pooling enables testing laboratories to get the most out of testing resources and overcome supply shortages. But there is also an accuracy tradeoff: Because pooling dilutes the nucleic acids produced by the SARS-CoV-2 virus, it creates the risk of false negatives. Pooled sampling is “most efficient in areas with low prevalence, meaning most results are expected to be negative,” the FDA noted in its statement.
To secure the EUA expansion for the SARS-CoV-2 RNA test, Quest provided the FDA clinical data showing that none of a total 3,091 specimens from a population with a prevalence rate of 1 to 10 percent would have come back falsely negative had the specimens been pooled. Quest began immediately to perform pooled sampling testing with the assay starting with its laboratories in Marlborough, MA, and Chantilly, VA.
It is no secret that laboratories lack the supplies and capacity necessary to meet the unprecedented demand for COVID-19 testing. Used effectively, sample pooling can go a long way in making testing available to mass populations while preserving testing supplies. As noted by FDA Commissioner Stephen Hahn “sample pooling becomes especially important as infection rates decline and we begin testing larger portions of the population.”
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