As states across the country grapple with an increase in coronavirus cases and a huge demand for tests, many businesses are looking for other ways to get more mileage out of their supply chain.
Like with anything else, supply and demand is a constant struggle. In this unprecedented era, the demand for things like coronavirus tests is so large that public health departments don't have a choice but to figure out ways to make our supplies last. Several states are examining pooled testing. California's Public Health Department says it's to "better leverage testing resources."
Pooling is something that blood banks have used for decades to keep their blood supply safe. Dr. Claudia Cohn is the Chief Medical Officer of the AABB, formerly known as the American Association of Blood Banks.
“If you have 100 people that need to be tested and if you test each of them, you’ll do 100 tests. If you find that your test is sensitive enough that you can pool together 20 samples at the same time, instead of having 100 tests, you can have five pools of 20,” Dr. Cohn said.
Now, if one of those five pools is positive, then Dr. Cohn says, "You’ll need to break it out and test each of those separately. So, let’s say you have one positive person in a pool of 100 people, you either do 100 tests and find one positive or you do five pools of 20, four of those pools will be negative, so you’ve done 4 pools and covered 80 people."
The test works by taking a tiny sample from each person who was tested.
“When you take a swab from everyone’s nose, you isolate the DNA from that swab,” Dr. Cohn said about the PCR test, which is generally a nose swab. “It’s not a lot, it’s a small amount but it’s enough. Because these tests are very, very sensitive.”
Those tests are so sensitive, and they have to be, that pooling can really only work if the test can handle, as in detect, multiple samples at once. The FDA mandates that.
“The FDA is quite demanding as they should be in terms of making sure tests work well and are safe,” Dr. Cohn said.
And Dr. Cohn says, pooling wouldn't work in an area where there's a large outbreak, which means a large number of people would test positive regardless of pooling. In the blood world, this strategy has been perfected.
“You are taking 100 samples and taking a drop from each sample and putting it together,” Dr. Cohn said. “You are testing every single person who comes through. In the blood world safety is before everything."
Blood banks test for HIV, Hepatitis C and B and well as COVID-19 antibodies, according to the American Red Cross. And, as this pandemic moves through our communities, Dr. Cohn says our blood supply needs to remain strong.
“After that initial spike, it went down again and that was okay because elective surgery had been canceled, so the demand for blood had gone down as well so for a while we were at a good balance of demand and supply. But then elective surgeries opened up and hospitals went back to full service and we’re in a shortage again,” Dr. Cohn said.