http://www.digitaljournal.com/tech-and-science/science/is-pooled-testing-the-answer-for-shortfall-in-covid-test-kits/article/575606

Is pooled testing the answer for shortfall in COVID test kits?

Posted Jul 30, 2020 by Tim Sandle
The U.S. has a shortage of COVID-19 test kits and locations for testing. Could this health emergency be better managed by pooling samples? There are pros and cons associated with this composite approach.
Coronavirus testing in the German municipality of Mamming  where an outbreak saw 174 seasonal worker...
Coronavirus testing in the German municipality of Mamming, where an outbreak saw 174 seasonal workers test positive
Christof STACHE, AFP
Although the level of coronavirus testing is around 750,000 individual tests per day, the demand continues to outstrip supply by a considerable level. This is particularly so in states like Arizona, California, Florida and Texas (states where there has been an upturn in the infection rate).
To address the shortfall in available test kits (and personnel to administer them), a solution that has been proposed by some scientists is to opt towards pooled testing. This approach involves testing small groups of people (the so-called "pools") using a single test. the advantage is that if a pooled sample is negative, then the inference is that everyone in the pool is clear of the virus. Conversely, if the result from the poll is positive for the virus then this means that every member of the pool will need to be tested individually.
Pooled testing
With pooled testing, a test center combines blood samples taken from multiple people and tests the individual specimens together in a pool to examine for the presence of genetic material that are indicative of the SARS-CoV-2 virus. A negative test for COVID-19 clears all patients in the pool.
The advantages and disadvantages of this measure will hang upon the chances of many pools being negative (which would require an understanding of which are the higher prevalence areas), as well as understanding any limitations around the pooled blood sample itself. There is a clear advantage in terms of delivering cost savings (the individual cost per test is around $100) and with speeding up the testing process.
To illustrate the extent of test savings in relation to different areas (from USC Schaeffer), based on current rates, pooled testing in Los Angeles (where 9 percent of people tested are positive) would reduce test use by around 50 percent.. In contrast, in Montana, where just 0.1 percent of the population is infected, adopting pooled testing could reduce test use by close to 90 percent.
There are risks with the pooled approach, according to Susan Bain of the USC School of Pharmacy, where a "potential limitation of pooled testing may result from dilution of positive samples, again resulting in false negatives. "
Bain also notes, in addition, that "those people who are asymptomatic or mildly symptomatic will have a lower viral load and, when pooled, may result in false negatives for the entire pool."