https://wet-robots.ghost.io/how-to-increase-covid-19-testing...
1) In your 94 well example, you'd need to dilute each individual sample 1/94. This could cause problems. The lower leveraged scenarios may be more useful due to lower dilution.
2) Similarly, very small scale liquid handling is relatively difficult to do. As you multiplex the number of sources into a well, the volume of each of those sources will decrease, increasing the difficulty and uncertain. Once again, a lower leveraged solution is likely viable.
It's also worth identifying that the bottle neck in testing is moving towards the availability of sample swabs, and reverse-transcription reagent (these happen up stream of PCR). Given those constraints, the emphasis should be on making all other steps in the detection chain as reliable (so simple) as possible to make the best of the bottle necked resources.
That said, it's a very clever idea.
The fundamental chemistry, as I understand it, is compatible with the method described by Dorfman.
I’ve actually reached out to MD Dr., biochemists, epidemiologists asking your very question: “Why can’t we mix samples?”
None seem unable to give me an straight answer. Most I’ve asked can’t get past the fact that you can still identify the infected individual after mixing the samples.
(Sorry dang. I know I’m banned. But I think coronavirus trumps a ban!)
[1] “the detection of defective member of a large population”
Nucleotide extraction and amplification are some of the most common contemporary applications of modern liquid handling robots. Cherry-picking or sorting of samples is also a technique that is common and well within the functionaltiy of these robots.
To avoid cross-contamination, diagnostic samples are typically not mixed and handled in discrete wells with sample specific disposable pipette tips. In a scenario where throughput/cost/reagent scarcity are important and false-positives (without severe symptoms) are low-risk I think your suggestion absolutely has merit. I am going to run this by our diagnostics specialist for further review.
I'd love to hear if this goes anywhere. My email is carlchatfield gmail com.
Thank you
"We need a mechanical device which can automatically sort the samples into well group"
PCR machines are actually not that complicated by comparison. Basically just a programmable heater.
Last time I looked into it (admittedly a while ago, so feel free to correct me), pipetting robots kind of sucked and weren't very precise.
Correctly handling tiny (microliter scale) fluid amounts without the slightest risk of cross contamination isn't going to be that simple.
But all that said, if you can solve this problem I think the idea is a real winner. Can be used for HIV and other PCR based testing as well.
I'm admittedly not the right person to implement this, and ideas are cheap. I just want to make sure the idea is out there.
I know there is a liquid handling machine made by CTC [1], which could handle very small volume of liquid, and do a lot of custom procedures.
Still, cross contamination is still a issue.
I don't think some liquid handling machine can outperform this.