I worked in the chemical industry. Some processes only worked on a relatively small scale. They were optimized by scaling-up the number of individual processes, rather than making the "vessel" larger. The output of the individual reactions was then combined and fed to one large downstream process.

Let's say we had 50 mini-processes feeding one large downstream process, we sampled the "composite" fluid from the mini-processes first. If we were out of specification, we then started sampling the 50 individual processes to find the culprit.

Why couldn't this be done for C-19 testing?

Let's say you had 20 employees at a healthcare facility. Could you get a daily composite sample and run one test for all employees? Then more testing if it's positive.

Seems this could work to also reduce lab testing in general. If you know the positive rate is say 1/20 test for a group of people, combine say 8 samples. Test composite and if positive, break it down to two sets of 4, and so on.

Sure, there's statistical optimization, but I'm just trying to suggest a process.

Sample size and lab equipment sensitivity are limiting factors, but it seems it would help the impossible "test everybody, everyday" issue realistically.

Again healthcare facilities would be the primary target to get "daily" testing of all employees in contact with patients.

PS: Thought about this about a month ago, when one of daily news conferences mentioned potentially testing wastewater discharge from a building.

Couldn't ABO blood type incompatibilies affect antibody results, even though the tests are run on serum. Combining nasopharyngeal swabs wouldn't make a lot of sense, would it? Group thermal scans for fever is technologically available now.

I believe that is how Wuhan just tested all 10m, they batched the tests then would do individual testing if positive results were found

terradactylexpress said:

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I believe that is how Wuhan just tested all 10m, they batched the tests then would do individual testing if positive results were found

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Thanks for the suggestion.

Googled "Wuhan batch testing" and got this article.

Wuhan tested millions of people for COVID-19 in just days. Could US cities do the same?

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But with pooled testing, a given population can be screened for COVID-19 periodically; that way, so-called silent spreaders can be identified and isolated, and their recent contacts can be alerted of potential infection, Frazier said.

"It's hard to have a scenario where you're testing every single person in a population," but the strategy could be particularly useful for screening high-risk groups, Zehnder said. Schools, nursing homes and correctional facilities, as well as populations of health care workers and first responders, could implement a schedule of pooled testing to spot outbreaks before they run out of control, he said.

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And for sample size:

Quote:

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Say you're testing 100 people and disease prevalence is 5%; with standard testing, you'd use 100 tests to test everyone and spot an average of five active infections. With pooled testing, you can lump swabs into groups of five and only use 20 tests in the process. Even if five groups came back positive and required retesting, you would only use 45 tests total as compared to 100.

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and

Quote:

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"This isn't new," Bilder said. Well-established methods of pooled testing now just need to be repurposed for COVID-19 testing, he said.

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Lots of good info in the article.

terradactylexpress, Thanks again for the heads-up.

There has been some suggestion of testing sewage effluent as a monitor of the virus in a population.

BoneBoy said:

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Couldn't ABO blood type incompatibilies affect antibody results, even though the tests are run on serum. Combining nasopharyngeal swabs wouldn't make a lot of sense, would it? Group thermal scans for fever is technologically available now.

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The swabs typically go into a solution to preserve the viral RNA. You could pool a portion of that from a group of swabs and then have a grouped sample.

However, the rtPCR tests generally are large scale tests, typically running 90+ samples at a time. Might as well just test 90 ppl.

The one at a time tests like the Abbott 15 min test, you stick the swab directly into the machine, so you can't pool for that one where it would actually be the most useful.

I'm interested in this pooled testing methodology as well as I think it is the only realistic way for schools and many businesses to continue. I'm just curious as to how it actually works, and why this couldn't be done for families as well meaning, instead of testing 6 members of a family individually, why not pool their tests since any pool found positive means the whole family is likely quarantining anyway.

However, I really am interested in knowing if pooled samples really are a valid reality.