I read an exchange on Twitter about pooled testing for COVID-19 and how other countries are using that technique to more quickly identify people who have COVID-19. Unfortunately, we are long past the point where pooled testing would work in the United States.
According to an FDA page on pooled sampling,
Pooling samples involves mixing several samples together in a “batch” or pooled sample, then testing the pooled sample with a diagnostic test. This approach increases the number of individuals that can be tested using the same amount of resources. For example, four samples may be tested together, using only the resources needed for a single test.
Nebraska actually used pooled testing in March, and it was apparently a cost-effective method of quickly testing large numbers of people.
If a pool of 25 samples were to come back negative, all 25 people could be declared infection-free, reducing the overall number of tests by 24. If that pool instead tested positive, a clinic could separate it into smaller pools — five pools of five samples, for instance — and retest. And if, say, two of those smaller pools turned up positive, the clinic could then individually test the remaining 10 samples. Even in the latter scenario, a clinic would save nine of the original 25 tests.
Nebraska eventually gave up on pooled testing for the same reason no one else in the United States is using it–it is only an effective method when the test positivity rate is relatively low.
The person who brought this up on Twitter mentioned its effectiveness in Rwanda, where the test positivity rate is currently at about 1.8 percent.
However, as of December 30, 2020, there is only one state–Hawaii–that has a test positivity rate of under 2 percent. Along with Hawaii, there are only four other states/districts with test positivity rates below 5 percent–Minnesota, Alaska, Washington, DC, and Vermont.
Idaho currently has a test positivity rate of 59.1 percent. California is at 12 percent.
When test positivity rates that high, there’s no point in doing pooled testing because the pooled test is almost always going to come back positive requiring further testing.
This is what happens when your country’s “leaders” count on a virus just disappearing like a miracle rather than make plans and following the science to minimize the impact of a pandemic.
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