In the United States, samples taken from patients through nasopharyngeal swabs and mouth swabs can now be bundled together and tested in groups at one of the largest commercial laboratories in the country,media The Verge reported. Quest Diagnostics, which handles tens of thousands of new crown tests a day, was granted permission by the U.S. Food and Drug Administration (FDA) over the weekend to test the collection.
This strategy helps to conserve resources by running multiple tests using materials that are typically required. It can also help Quest avoid backlogs and move inspections faster. Currently, the demand for testing in the U.S. is so high that Quest Labs takes an average of seven days to get the results to patients.
However, the strategy does not clear all detection roadblocks and may not work well in areas where testing is most needed: flash spots where detection resources are scarce. In these environments, if a high percentage of test results are positive, the aggregate test will ultimately not save material — too many positives, meaning more retesting.
“When the positive rate is high, the set test is not very effective because you have too many tests to do, and it’s not worth your effort.” Peter Iwen, director of the Nebraska Public Health Laboratory, said.
Quest’s method will combine samples taken from four people. If the multi-sample test is negative, all four are considered negative. If it is positive, each sample will retest itself to find out who has the virus. The company said in a press release that it will begin launching assembly tests at its laboratories in Chantilly, Va., and Marlborough, Mass., over the weekend, and then expand to other locations. Quest did not respond to a request for comment.
Experts in the United States have been interested in set-up testing for the past few months. This method has been widely used to screen people for sexually transmitted infections, and it is also used to check for diseases in blood donations. Deborah Brix, a member of the White House’s Coronary Virus Task Force, told a meeting of the American Society for Microbiology last month that the strategy could dramatically increase the number of daily tests in the United States.
As early as March, Iwen began exploring a collection of tests at nebraska public health laboratories. He used fewer and fewer chemicals to run each test, and he knew he could save them by grouping samples. He conducted some experiments and found that he could do it successfully. “It works well and I can save 60 to 70 percent of our reagents, ” he said. He obtained the approval of the governor of Nebraska to move on in their state of emergency. “We started gathering, and we were able to keep the lab running,” Iwen said.
Nikhil Gopalkrishnan, a postdoctoral researcher at Harvard University’s Wise Institute for Biological Inspirational Engineering, says the shortage of testing materials is just one type of obstacle that a collection test ingenuity strategy can help overcome. But supply shortages are not the only thing holding back testing. “Depending on what the real problem is, collection detection can have a real impact, or it may not,” he said. “If it turns out that they’re short of staff, they just don’t have enough people, and the limiting factor is that someone has to unscrew all the tubes – the collection test won’t be there to help you.”
Once the infection rate in the community starts to rise, the collection tests do not help. Iwen had to stop using the Nebraska lab’s collective testafore a few weeks ago because the rate of positive tests was too high — more than 10 percent. In any set of random four or five tests, there is a good chance that one is positive. If the positive rate is so high, collection testing often does not save a lot of chemicals or time.
If 13 percent of a laboratory test is positive, the lab should reduce the size of the collection test to three, according to a new instruction for Quest collection testing. If 25% of the test results in a laboratory are positive, they should not be tested for collection. Virginia and Massachusetts were among the first quest labs to be set up for set-up testing, with positive rates of about 6% and 2%, respectively. In one of the hardest hit states, Arizona, its positive rate is about 24 percent.
Iwen says it’s possible to make aggregate testing work in an area with a high percentage of positive tests. If they have information about the patient (if they have symptoms, where they live and where they work), they can classify the patient.
Iwen adds that this will only work if the lab has access to good demographic information about the samples they test. But usually, the lab gets samples without knowing where they come from.
Despite these limitations, Gopalkrishnan says Quest’s authorization is a good first step toward broader collection detection. He would like to see a larger pool of detection, especially in areas where COVID-19 does not spread much. Increasing collection detection to dozens of samples, or up to 100 samples, can help the lab process samples faster. “I think you’ll see more collection detection authorizations come in,” he said.
Iwen believes that properly implementing collection detection can help detect faster. “It’s a process that needs to be considered if we’re going to do tests that have been required for the lab,” he said. “Turnaround time is important, and if it has an impact on that, it’s worth it.”