Why Pooled Testing for the Coronavirus Is not Working within the U.S.

Why Pooled Testing for the Coronavirus Isn't Working in the U.S.

Pooling makes up about a third of the samples processed at Poplar, Sweeney said, adding "that percentage will get much higher".

In many other regions, however, experts have problems overcoming the hurdles in order to benefit from pooling – also because the needs are so different from institution to institution and even from test to test.

"There were many concerns about all of the challenges," said Dr. Bobbi Pritt, director of the clinical parasitology laboratory at Mayo Clinic, which runs tens of thousands of coronavirus tests every week but has not yet implemented pooling.

For example, experts do not agree on the threshold above which pooling no longer makes sense. The Centers for Disease Control and Prevention's coronavirus test, used by most public health laboratories in the United States, states that pooling should not be used when positivity rates exceed 10 percent. But at the Mayo Clinic, "we would have to start questioning this once the prevalence is over 2 percent and definitely over 5 percent," said Dr. Pritt.

And prevalence isn't the only factor. The more individual samples are grouped, the more efficient the process becomes. But at some point the advantages of pooling will reach a turning point: A positive sample can only be diluted so much before the coronavirus can no longer be detected. This means that when pooling, some people will be missing who contain very small amounts of the virus.

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frequently asked Questions

Updated August 17, 2020

  • Why does it help to stand three feet away from others?

    • The coronavirus spreads mainly through droplets from your mouth and nose, especially when you cough or sneeze. The C.D.C., one of the organizations using this measure, bases its six-foot recommendation on the idea that most of the large droplets that people make when they cough or sneeze fall within six feet of the ground. But six feet has never been a magical number that guarantees complete protection. For example, sneezing, according to a recent study, can trigger droplets that are far farther than two meters away. It's a rule of thumb: it is safest to stand six feet apart, especially when it's windy. But always wear a mask even if you think they are far enough apart.
  • I have antibodies. Am i immune now?

    • As of now, this seems likely for at least a few months. There have been appalling reports of people apparently suffering from a second attack of Covid-19. However, experts say these patients may have a lengthy course of infection, with the virus taking a slow toll weeks to months after initial exposure. People infected with the coronavirus typically produce immune molecules called antibodies, which are protective proteins made in response to an infection. These antibodies may only last in the body for two to three months, which may seem worrying, but that's perfectly normal after an acute infection subsides, said Dr. Michael Mina, an immunologist at Harvard University. It may be possible to get the coronavirus again, but it is highly unlikely to be possible in a short window of time after the initial infection or make people sick the second time.
  • I am a small business owner. Can I get relief?

    • The stimulus packages passed in March provide help to millions of American small businesses. Eligible are companies and non-profit organizations with fewer than 500 employees, including sole proprietorships, independent contractors and freelancers. Some larger companies in some industries are also eligible. The assistance offered, administered by the Small Business Administration, includes the Paycheck Protection Program and the Economic Injury Disaster Loan Program. But a lot of people haven't seen any payouts yet. Even those who have received help are confused: the rules are draconian and some are stuck on money that they cannot use. Many small business owners get less than expected or hear nothing at all.
  • What are my rights if I am worried about going back to work?

  • What will the school look like in September?

    • Many schools are unlikely to return to a normal schedule this fall, which will require online learning, makeshift childcare, and stunted work days to continue. California's two largest public school districts – Los Angeles and San Diego – announced on July 13 that classes would only be held remotely this fall, citing concerns that the rise in coronavirus infections in their areas is too great Poses risk to students and teachers. Together, the two districts enroll around 825,000 students. They are the largest to date in the country, abandoning plans for a partial physical return to classrooms when they reopen in August. For other districts, the solution is not an all-or-nothing approach. Many systems, including the largest in the country, New York City, are developing hybrid plans where some days are spent in classrooms and some days online. There is still no national guideline on this. Therefore, check regularly with your city school system about what is going on in your community.

“Will we cause harm if we miss them? I think that's still a difficult question to answer, ”said Dr. Liesman. These people may be less likely to pass the virus on to others and have a lower risk of getting seriously ill. However, this is not a guarantee. Some could just be early in their infection.

Pooling can also be a nuisance for lab technicians – many of whom have worked strenuous hours for months. Although theoretically simple, batching samples is tedious and time-consuming as researchers transfer precise amounts of liquid from one tube to another hundreds, perhaps thousands of times.


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