Faced with the biggest coronavirus outbreak in the world and long wait times for test results, the Food and Drug Administration on Saturday issued the first emergency use authorization for covid-19 pool testing, a form of testing that allows up to four samples to be tested at once using the same test.
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The real-time PCR pool test belongs to Quest Diagnostics, the largest private medical testing company in the U.S., which recently stated that the average wait time for people who are not considered priority patients is seven or more days. The company does not expect to reduce those wait times as long as covid-19 cases continue to increase dramatically across the U.S.
In its press release announcing the emergency use authorization, the FDA said that sample pooling is an important public health tool because it allows for more people to be tested quickly using fewer testing resources. Instead of using an individual test on every sample, pool testing analyses multiple people at once using just one test.
In this case, up to four samples are tested in a pool. Per the FDA, if the pool is positive, it means that one or more of the people tested in the batch may be infected. Should this situation arise, all of the samples in the pool are tested again individually. The FDA highlighted that this technique is expected to save testing supplies, which is another problem labs face.
“Because the samples are pooled, it is expected that fewer tests are run overall, meaning fewer testing supplies are used and more tests can be run at the same time allowing patients to receive their results more quickly in most cases,” the FDA stated.
Quest Diagnostics, for instance, has said that global supply constraints continue to be an issue, a factor that limits how quickly it can increase testing capacity. Although the company maintains that its suppliers of test platforms and reagents continue to be responsive to its need to add capacity, “they are limited amid surging demand in the United States and globally.”
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Quest Diagnostics said this past week that it currently has the capacity to run 125,000 molecular diagnostic tests a day, roughly double the capacity it was at eight weeks ago. It expects to have the capacity to run 150,000 tests day by the end of July.
Nonetheless, this new testing technique isn’t the final solution to America’s testing woes and isn’t suitable in all situations. The FDA says that this technique is most efficient in areas with low prevalence, or areas where a low amount of people actively have covid-19.
The agency also addressed concerns that testing multiple samples would make it more difficult to detect positives, “since pooling in the laboratory dilutes any viral material present in the samples.” However, it said that the validation data Quest Diagnostics provided the agency to receive its emergency use authorization demonstrated that its test corrected identified all of the pooled samples that contained a positive sample.
Quest Diagnostics stated in a press release that in the clinical data presented to the FDA, none of the 3,091 specimens with a prevalence rate of between 1-10%, if pooled, would have been incorrectly determined to be negative. The company stated that pooling is frequently used in blood banking to screen donated blood for a variety of viruses.
Jay Wohlgemuth, senior vice president and chief medical officer at Quest Diagnostics, applauded the FDA for allowing it to use its covid-19 pool test. However, he also warned that it was not the way to fix America’s testing problem.
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“Pooling will help expand testing capacity but it is not a magic bullet, and testing times will continue to be strained as long as soaring covid-19 test demand outpaces capacity,” Wohlgemuth said in a statement. “Each of us can practice behaviours that will reduce covid-19 infections in our communities, so our national healthcare system can better respond to this crisis.”