Pooled COVID Testing
25 Feb 2021

The Dangers of Depending on Pooled COVID Testing

The idea of pooled COVID testing seems like a great idea at first glance, but it comes with its own set of issues. The CDC defines COVID test pooling as “combining respiratory samples from several people and conducting one laboratory test on the combined pool of samples.”

Pooling allows laboratories to test more samples with fewer testing materials – Which means that more people can be tested in locations where testing resources are limited. Testing has been touted as one of the best ways to prevent the spread of the virus. Yet, throughout the pandemic, access to testing has often been limited, people have had to wait in long lines, and results have been delayed at times for several weeks due to a backlog of tests at laboratories.

Ideally, pooled testing could reduce backlogs by combining groups of samples to be tested all at once. The process is as follows:

  • If a pooled COVID test result is negative, then all the samples can be presumed negative with the single test.
  • If a pooled test result is positive, each of the pool samples will be tested individually to determine which are positive.

It is recommended that pooled testing only be done on small groups of people such as families or workers returning to a common office. According to Smithsonian Magazine, researchers reported that pooled COVID testing is approximately as accurate as individual testing for pools that include up to eight samples. Proponents of pooled testing also note that it can be an inexpensive option because of the reduced cost of a single lab test for multiple people.

The Problems with Pooling

Unfortunately, there are problems with pooling COVID tests. The CDC specifies that “pooling should only be used in areas or situations where the number of positive test results is expected to be low—for example, in locations with a low prevalence of SARS-CoV-2 infections.” When infection rates are high, too many pools come back with positive results.

This would require more individual tests, thus making the pooling method less efficient and more complicated.

Contagion Live, a news resource covering all areas of infectious disease, recently reported a number of additional issues with the pooling strategy. Research has shown that pooled COVID testing can increase the number of false-negative cases (when someone who is infected with the virus falsely tests as not having it) as well as decrease the sensitivity of COVID-19 detection, especially in people who are asymptomatic or had a low viral load.

Obviously, false negatives can increase the risk of an outbreak, defeating the whole point of testing. Additionally, while pooled testing can decrease the number of tests needed, the need to retest all the individuals in pools that tested positive lessens the decrease (and expense savings).

According to the article, “Pooled testing is useful for population screening and resource-restricted settings, due to its ability to stretch COVID-19 testing supplies, increase the number of patients tested, and increase the number of cases detected. However, there are drawbacks, including the complicated workflow, lower sensitivity, and the need to repeat tests from positive pools.”

If your business is considering utilizing a pooled COVID testing strategy, you should be aware of the drawbacks. Consider other solutions to mitigate the risk of an outbreak that can help you protect your customers, guests, and employees when used in combination with recommended best practices. Visit our website or contact us to learn more.

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