NEW YORK, July 24 (Reuters) – US health officials, including Deborah Birx, coordinator of the White House Coronavirus Task Force, called for the so-called pooled tests to diagnose COVID-19 to test more People faster and reduce mounting response times for results.
Quest Diagnostics received the first emergency authorization from the US Food and Drug Administration on Saturday to use pooled tests to help reduce its accumulation of COVID-19 tests. The following is a description of how it works and the advantages and disadvantages of grouped testing.
How do grouped tests work?
In pooled tests, the labs combine samples taken from multiple people and analyze the multiple samples together to detect the presence of genetic material from the new coronavirus. If a batch is negative for COVID-19, all of those patients are eliminated. If a lot is positive, samples should be retested individually or in smaller groups.
Such tests could be used to quickly eliminate groups of people who are not likely to be carriers, such as students returning to school or individuals in areas with relatively low levels of active COVID-19 infection.
“This type of test works really well when you have a population of asymptomatic patients or are following up on contacts where the likelihood of someone having the SARS-CoV virus is pretty low, because you could test multiple groups and get tons of negatives.” said Carmen Wiley, president of the American Association for Clinical Chemistry (AACC).
What are the benefits of grouped testing?
US independent laboratories and hospitals are struggling to meet the growing demand for testing as infection rates increase in many parts of the country. Waiting more than a week for results, which has become common, defeats the purpose of trying to slow the spread of the virus by identifying who can be contagious before they can infect others. Pooled tests may alleviate some of that problem.
If a laboratory analyzed a batch of 12 samples, one of which was positive, it could analyze smaller batches of four samples each. The smallest group with the positive sample would be analyzed individually to identify the infected person. That process requiring seven tests is still a 42% reduction compared to 12 individual tests.
Fewer tests not only means faster results, but also releases scarce test materials, such as chemical reagents.
What are the drawbacks?
If the disease is prevalent in a community, more than about 10 percent, according to the AACC, pooled tests are no longer useful because so many follow-up tests are likely to be required.
Pooled tests can also lead to an increase in false negatives because pooled samples are diluted, making it harder to collect virus material, according to the FDA. Quest, however, says that in the clinical data he submitted to regulators for his pooled testing method, he would not have found a false negative in more than 3,000 samples in total. (Report by Michael Erman; edition by Peter Henderson and Bill Berkrot)
