Well, this blew up (thanks, Steve Mould!) so I’ve not got time to reply to every comment individually, but I thought I’d stick a quick FAQ up here as a few things keep coming up! *How does this actually work in practice?* When the swabs arrive at the lab, they get dunked into some liquid to extract the RNA. (No further questions, I’m a _computational_ biologist! ;) ) You can then pipette small amounts of this liquid into wells to mix them together, and/or keep a small amount of it back to do a second test later if needed. We don’t need to do multiple swabs, thus delaying matters, and we definitely don’t need to stick a potentially coronavirus-y swab up multiple people’s noses!! *Does this affect test accuracy?* I thought this was too complicated for an already-long video, but you asked. :) The short answer is: probably not! The obvious worry is false negatives, because you’re mixing samples together and diluting them so maybe you’d miss cases. I read a few papers which went into detail on this, including this one: advances.sciencemag.org/content/6/37/eabc5961 It's for the P-BEST algorithm, and they check the test sensitivity with real PCR tests, and conclude it doesn't affect false negatives too badly. Another problem is false positives. However, combinatorial testing should reduce false positives: imagine you got a false positive in one pool, you might then have (say) three other pools containing each of the samples in the positive one to clear their name! Depending on the biological details you might then want to re-test those samples just to be sure, but either way I think it should reduce the false positive rate. *Why aren’t we doing this?* I don’t know. There are some logistical issues, but unless they make things ten times worse in the lab we’re still winning! *Update:* With fantastic timing, the Rwandan group's paper on hypercube-based test pooling is published in Nature today! www.nature.com/articles/s41586-020-2885-5 Thanks for watching, and if you’ve got any more questions that aren’t covered above feel free to stick them here and I’ll try to answer!

@anthonylosego

3 жыл бұрын

Woh! Woh! Woh! Woh! Woh! Woh! Woh there buddy!!! Don't you start using "logic" on us now! We've done just fine using our alternative logic thank you very much! Besides, where ya gonna get all these "Mathsy" type people anyways? We don't hardly have enough of them here in the states to make a dent in any of our processes. So there! (Okay, this was sarcasm.) These ideas are awesome. And yeah, they could do well, but really, it has to also be followed up with a complete no brainer way of ensuring the average person conducts the procedures correctly. They won't understand why they are doing it, so making silly mistakes will be inevitable. Yes, it COULD work, in theory. But humans are at every facet of this approach. To factor the error potential out may very well be impossible. Perhaps if we had robots doing human jobs, not just in a lab, but all up and down the work environment, yes, then maybe that will work. But we're not exactly there yet. Robots are barely faking it at the moment. (See recent robot conventions on youtube, not too impressive [for bridging the gap to replace humans that is]) Should we not try? Heck, sure why not? I'm not sure we could make it much worse than it already is (in the USA at least, France and Italy aren't looking so hot either).

@Xeldur

3 жыл бұрын

I can't help but feel that maybe we are lacking tools to make this easy enough for the layman. We can't assume that swab testers have the knowledge to perform combinatorics math reliably. Even though it does sound like they should know how...

Steve Mould sent me here. (He's a wise man.)

@DrAndrewSteele

3 жыл бұрын

He really is. Everything I know about Pythagorean siphons I learned from him.

@Taka.1011

3 жыл бұрын

Same

@stridenbear

3 жыл бұрын

Same

@haythamfpv2797

3 жыл бұрын

I've never looked at my flush the same again

amazing! found your video through steve mould

@dariodalcin5177

3 жыл бұрын

yep

@TomLeclerc

3 жыл бұрын

yep

@ERROR204.

3 жыл бұрын

yep

@inigo8740

3 жыл бұрын

Yep

@declaniii6324

3 жыл бұрын

yep

Thanks Steve Mould 👍

@DrAndrewSteele

3 жыл бұрын

I agree! What a guy!

I got really emotional watching this. It's so nice to listen to someone who's not a complete bumbling obnoxious plank talk about Corana Virus for 15 minutes. Great Stuff!

@StefanReich

3 жыл бұрын

He starts out with "the coronavirus pandemic" as if it was real. Sorry can't take him seriously.

@user-qx7tm5df8j

3 жыл бұрын

@@StefanReich lets just hope you are joking.

As an analytical chemist, one reason pooled testing isn't used in most instances is because of two factors: 1) false positives. If you have a false positive in a situation where you are testing 1:1, you only need to retest that one sample twice to correctly identify the false positive. If a pooled result comes back as a false positive, you would then have to test all the individuals in the pool twice (and possible retest the pool as well) to comfortably confirm it was a false positive. 2) capacity. If you are pooling tests, and at maximum capacity, and then you get (either by chance or by rates going up) an increase in positives, you then need to do a lot of extra testing you don't necessarily have capacity for, meaning the lab becomes overwhelmed (which is the worst thing to happen as positive rates increase). 1:1 testing more or less assures this can never happen

@x--.

3 жыл бұрын

This all makes sense but I think some out of the box thinking here may be helpful. That is to say *completely supplementary* testing. Right now we only have the labs and testing for people who exhibit symptoms or have some high-risk which means regular testing. If we spent the money to add lab capacity to do *this* kind of testing then we could do 'test everybody' type regime that could help detect hot-spots very quickly and give groups some indication of risk. And would that be enough to open up? ... Well, probably not. The lag time is probably still too great and the ability for quick spread too high for this to be enough as the virus is spreading quickly -- but maybe back in the summer months it would have been just the thing to really stamp out the virus so there were fewer active cases going into late fall and winter. So basically, I talked myself out of this being a solution now (for this pandemic anyway, on the assumption we have a widespread vaccine in April/May). Still fascinating math! :)

This is how the University of Cambridge is managing to provide weekly asymptomatic tests to students. Apparently experts seem to be pretty good at doing stuff

Love this I wish this wasn't all so politicized and we took a more mathematical approach

@mariobros7834

3 жыл бұрын

@Jitwitdastick JRE III yeah? In my country it is the other side who bought a shady Chinese vaccine with taxpayer money without any kind of auditing and now wants to use the police to force people to take it. Suddenly it is your body, their rules.

@wizzerd229

3 жыл бұрын

@@mariobros7834 sure thing. I'm sure that's happening

@ulti-mantis

3 жыл бұрын

It's hard not to politicize it when there are groups that don't believe in math.

@JayTie1

3 жыл бұрын

Germany does exactly this

You may be interested to know that the University of Cambridge is using a pooling method for its weekly testing and these pools are comprised of households (people who share facilities so are counted as in the same bubble like a family which shares a house) which means that positive test results are likely to be grouped together further increasing efficiency.

@antisocialbob968

3 жыл бұрын

For those who want to know more they actually group the tests on a more fundamental level than in this video as we all put our swabs into the same testing tube (I am not currently familiar with exactly what happens when a test comes back positive but it may well be the case that they send out a new set of tests to be done from scratch again - this extra delay not being a problem as if someone in your household is positive everyone needs to isolate anyway)

@notme-ji5uo

3 жыл бұрын

@@antisocialbob968 wait so everyone gets swabbed individually but the samples get tested as one?

@antisocialbob968

3 жыл бұрын

@@notme-ji5uo yes all the individual swabs which are from each of the (up to 10) people get put into the same testing tube so I don't see how they could separate out who is who

Also. If the pools are “contact groups”, for example , families ,work groups or passengers, etc. . you probably don’t need to test individually everytime. Since you will need to isolate all of them anyway in case they have the virus but it’s still not enough for the PCR to detect. In that case. You can treat all the group as positive an test another “layer” of contacts of all the members of that group in order to try to find new possible cases sooner.

Found this on Twitter and regardless of the subject matter it’s the first time I’ve found maths remotely interesting since (or more likely because of) school. Perfect choice of T-shirt too! 👏🏼💪🏼

@samrusoff

3 жыл бұрын

I was trying to figure out what the shirt represents, where's it from?

@LeedsGuy

3 жыл бұрын

@@samrusoff it’s a moon phases t-shirt but it’s also very similar to the 91 sample tray mention in the vid. No idea where he got it from though, sorry.

2D pooling also reduces false negatives because every sample gets tested at least twice. This is awesome!

Please almighty KZread algorithm, let this go viral. People making decisions need to know this

I'm new to the channel and had to double check for a moment that the subscriber count is actually 1,6K and not 1,5M

The pool method of testing has long been implemented when giving blood in Belgium. This also gives you the option to decide yourself whether you want an extra (for example hiv) test when you get a letter that your pool was found positive.

Great video! Nice graphics, really easy to follow. Good on ya, mate.

This was great, subbed! Hi from Steve Mould!!

Steve Mould sent me here too. Very well done !!! Thanks !!!

Brilliantly explained. And fascinating. Send to Boris Johnson immediately!! Thanks Steve Mould for the heads up in this!!

Amazing Video! Math should rule the world! P.S Thanks for "Video chapters".

Just got this in my KZread recommendation. Godspeed, brother.

One of the most underrated channels out there with video production better than that of channels with 1M+ subscribers! Proud to say I was watching you before you inevitably blow up Andrew!

@DrAndrewSteele

3 жыл бұрын

Haha thank you! Hope you're right :)

Awesome info. Thank you

Great up n coming channel it would seem, thanks Steve Mould for the recommendation

A joy to consider such mathtastic measures, thanks

Hi, in Australia this is how we've been doing pcr testing since march

Liked, subscribed, thank you for pointing this out, and thanks Steve Mould for pointing you out.

Very well explained!

Great video, more visual aids for the situations you're talking about please. Even simple visual aids

@DrAndrewSteele

3 жыл бұрын

I'll see what I can do! This was a really hard one to animate in places but I am definitely a fan of using visual aids where possible-otherwise, why not just make a podcast? :)

Nice video, really well put together

@DrAndrewSteele

3 жыл бұрын

Thank you!

Love this! Excellent!

Simple and clear. Great explanation, you're very talented at making informative content! I was very surprised seeing at the end of the video how few views it has. I hope your channel grows (with a little help from Steve Mould)!

@DrAndrewSteele

3 жыл бұрын

Thanks! And always happy to have a leg up from the mighty Mould!

@tommyvega7948

3 жыл бұрын

@@DrAndrewSteele he is one of the nice guys of KZread! Well, I did my part by subscribing! Off to check your other videos!

@DrAndrewSteele

3 жыл бұрын

@@tommyvega7948 Thanks dude, hope you enjoy!

This is a bit like error correction in coding theory. Very interesting!

Brilliant. Why I didn't think of this before. It is so obvious.

Really great explanation. It is frustrating to think of the usefulness of such strategies, especially the more simple to understand ones, aren't being used more prevalently. We can only hope this changes.

Brilliant!

This needs to be seen by more people

This sounds like a spreadsheet I made once. Teachers have to do supervision of students at lunch and recess. The problem is that the teachers hate giving up their break time. There are a total of 10 areas that need supervision sometimes at the same time. The teachers don't want to do supervision 2 days in a row, or the same area more than once in a row and certainly not twice in the same day. They also can't do certain areas or times due to schedule conflicts or other factors. There could also be prefences to avoid certain areas but not a hard no. You also need to make sure that nobody does more or less than their fair share so if a few had to do more than average one month they will do less in the next month to balance it out. Oh yeah and not all teachers are full time. Some are half time and one is .6 time. Let me know if you want to know how I solved this.

i work with one of the Alinity machines (the high-volume covid analyzers) we tried pooling samples at one point, but due to the volume of tests, the limitations of the instruments, lack of fully-automated workflow, and the hospital's treatment/isolation schedule being dependent on the turn around time of these tests, we've found pooling samples to be troublesome and inefficient.

@klausbrinck2137

3 жыл бұрын

surely the system isnt build around pooling...

@microArc

3 жыл бұрын

@@klausbrinck2137 that is correct in the majority of cases. that being said, some companies/systems are willing to/already have re-formatted their workflow to run in such a way. of course, changing so dramatically costs money and more importantly time. it may also require retraining of staff.

Nice video. Headline: Block Designs allow efficient characteristic evaluation shocker... who'd have thunk combinatorics had any practical use (except for Marketeering people for the last 50 years)

I don't know what pooling strategies are used here in Sweden, but I do know pooling is used.

That was a very interesting video! I dig it

From what I understand, one issue with such massive testing is how to collect the test samples. There are already often queues in front of testing facilities and people have to wait to get tested. Nevertheless, I absolutely love the presented ideas!

I like this video. Thanks. I subscribed.

That strategy is implemented in Denmark. We're pooling three samples at a time, but that is more in order to reduce spent test kits. Worst effect is that a person who is positive gets their result later.

Great video!

Clicked on the video only because I own your shirt! Its a good shirt!

This was actually... Really good wow

THIS IS SO COOL! It's incredibly frustrating that this isn't being done. All of the people complaining that they want to go get a haircut and go to the movies could do that if we tested everyone! Imagine! We could go back to normal!

I'm not usually one to leave KZread comments but I just wanted to say this video was great! Just subscribed and look forward to more of the same, and yes Steve sent me :p

This reminds me of the 1000 bottles of wine riddle

Brilliant

The limiting factors will end up being swabs and PPE if this is used as a broad test of the population. You can get around the PPE by having people swab themselves under supervision. Not sure about the swabs if we test very large portions of the population regularly though.

Watched this several hours ago and I'm still trying to decipher the t-shirt.

@TSutton

3 жыл бұрын

Me too! At first thought it was something to do with phases of the moon but I’m not so sure...

@kukunishad

3 жыл бұрын

@@TSutton Solar Eclipse phases..

@DrAndrewSteele

3 жыл бұрын

@@kukunishad Haha, all good suggestions! I too have spent lots of time trying to work out what it means…

@kukunishad

3 жыл бұрын

@@DrAndrewSteeleReally?? I thought you like astronomy so you wore that tshirt :D

@DrAndrewSteele

3 жыл бұрын

@@kukunishad Looking ambiguously astronomical was definitely a big factor in its purchase!

Awesome video! What happens when we factor in false negative and false positive rates?

Struggling to understand why this isn't implemented... It's very frustrating How robust are these methods when considering how false positives/negatives will propagate? Its the only thing I can imagine being a problem. I know the PCR test is meant to have very high sensitivity and specificity but the values are always going to be imprecisely known given how cross contamination is so unpredictable. I still hear the argument it's best to avoid testing populations expected to have very low prevalence of covid due to the whole Bayesian problem where number of false positives becomes significant compared to true positives. But it should be possible to put an upper bound on the specificity of the PCR test so far at least given the lack correlation between tests administered and number of positives cases.

@DrAndrewSteele

3 жыл бұрын

Yeah, it really is. It's taken me a while to get round to making this video too-people have been going on about it for months! Sorry to copy/paste a reply but this from another comment hopefully answers your question: You're right that it makes things more complicated-too complicated for my video, I decided! :) I read a few papers which went into detail on this, including this one: advances.sciencemag.org/content/6/37/eabc5961 It's for the P-BEST algorithm, and they actually check sensitivity with real PCR tests, and conclude it doesn't affect false negatives too badly. I think combinatorial testing should reduce false positives, as you'd have multiple other pools containing any given sample to clear their good name as it were!

@microArc

3 жыл бұрын

this isn't implemented because it creates a very difficult workflow to keep track of pools and test groups. it's a very good idea on paper that translates poorly into a real lab environment. other stuff: a glaring issue of using % of positive tests is that many patients are tested multiple times due to false positives/confirmation testing, and even duplicate testing. false positives can be caused by similar DNA/RNA sequences that are similar to COVID's. PCR errors are sometimes unpredictable and uncontrollable due to transcription errors made by the enzymes used in the PCR testing. tests in the medical field (in the USA) are run with 95% confidence intervals, meaning they are reliable 95% of the time, verified by QC every 24 hours. if the test cannot meet this criteria, it is not suitable for mass-scale testing. i work with the one of the major Alinity instruments used for mass testing of COVID samples in USA.

@Konfusette

3 жыл бұрын

While this Video and the work behind it is great, it is problematic that the reasons why this way of testing is not feasible in a lab environment are just brushed over. As stated by the comment above, the work flow of this is too complicated and "just using robots" makes this whole issue seem like everything we need is available but politicians are just too blind/lazy to implement this. One of my friends set up and operates one of the "usual" testing robots - a highly complicated matter and it does not always run smoothly. Get this unsmooth operation, false positives and negatives, etc. into one pot and you're headed for disaster. One thing mathematicians and also physicists sometimes just brush over in their proposals is if their theories can actually be put to work as easily as they think (which usually isn't the case). This video frustrates people that have no background in how the testing works, what further problems come with this proposed method and leaves them feeling quite right in their opinion that our governments just suck/are dumb.

@DrAndrewSteele

3 жыл бұрын

​@@Konfusette Thanks for the comments, Nico and Aaron! I freely admit I've not gone into detail here (and I'm a dreaded computational biologist who's never used a pipette), but smarter wet lab people than me think this is viable and I trust them! The logistics aren't totally straightforward, sure, but unless they make testing ten times harder you're still winning! The robots remark was a bit of a throwaway. :) One more practical idea for humans I've seen are these 'origami assays' which use printed and punched cue cards to guide where to drip samples onto a plate for combinatorial testing, see www.smarterbetter.design/origamiassays/default/instructions I did have a mention of this in the original script but it was just getting too long!

@microArc

3 жыл бұрын

@@Konfusette not only is the operation not very smooth, but there is a massive shortage of Clinical Laboratory Scientists right now. there's a 20-30 year age gap in the work force. if nurses and doctors are the stars of the show in medicine, clinical laboratory scientists are the stage crew. no screen time, but the show wouldn't work without them.

Interesting stuff. Steve sad Hi. Subbed.

BRILLIANT.

binary search is so amazing 🔥 Still many countries are not permitting for the pool testing :(

Great idea/ But would it not make sense to use hexadecimal numbers? Test 16 (or 32/64 etc...) If negative - clear. If positive - split - test 8. If negative, clear. Test 4. If negative, clear. In the case of positive - split and test half. Repeat. This way you could combine any number of samples and eliminate any clear group. Any positive group would be split and retested.

Could this be done for testing a sample size of 200 i.e. a commercial flight?

The only problem with this calculations is that it totally ignores the fact the lab testing is only one part of the problem , the real bottleneck timewise is the nasal sample collection as people must be handled with significant time and space separation to avoid contamination.

Is it group testing? I just wanna guess. I'm excited.

Great video, sound needs to have more treble and a bit of reverb.

How would any individual test error resulting in, false positives, and false negatives, affect the maths?

@nulle8935

3 жыл бұрын

I don't think it would effect it that bad

I couldn't find a totality on his T-shirt 😅. I want this T-shirt 😍😍

I've heard of some of these ideas before but not fully had them explained so interesting to hear a bit more detail. However, some of these ideas require diluting the sample and I wonder how much this will affect accurately identifying actual cases. PCR doesn't give a binary answer. PCR involves repeated cycles to amplify the viral genetic material. If the viral RNA is detected within a set number of cycles the sample is said to be positive. If your sample is divided (e.g. one for pooling and the other for confirmation or divided into two separate groups) arguably that would require more cycles to detect the virus and then actually increase the chance of a false positive due to background noise.

@DrAndrewSteele

3 жыл бұрын

This isn't as much of a problem as it seems-see the FAQ in my pinned comment!

This is clever Idea but the consistency of the sample contains this RNA will be hard to find. Maybe ?

In theory you could use even less test as say a group of 8 people test Positive then test in 2 groups for each half then test the 2 remaining and and then you only used 4 tests in a senerio that you describe would use 9 the problem is it would increase the time for results exponentially since you would have to have the larger group tested before the smaller ones it would take more time so the real problem is which you want to value number of tests or time to get results

Basically the same idea as hamming codes

Surely you can do some kind of binary search here? That would only require O(k*log(n)) tests for pools of size n, with k positive cases.

Nice approach.. seems kinda obvious that it should be implemented. But what about false negatives? The impact of false negatives would have much greater impact using this methods. Still though, you could run 2 of these tests a week apart and use less tests than the default case.

Love the maths. They are doing this to a certain extent in the UK, testing students and sticking all the swabs into the same sample from the class. If a class comes back positive the hole class is tested again, indevidualy.

Not once did you take into account dilution factor from multiple samples and the need to run the PCR for a higher cycle count.

I thought about something similar when testing blood samples from donation for infected samples (HIV e.g.). Since I'm Software Engineer, I am familiar with binary search and know its advantages.

What about Hamming code for multiple error detection that could possibly lower the number even more.

How would these methods deal with false negatives? Would the overall false-negative-rate increase?

its the same algorithm of an led screen, how we control each pixel.

What about using a binary mapping?

There’s a strong connection between this and error correcting codes used to make digital transmissions error correcting and error detecting. 3blue1brown’s recent videos on the topic do a great job speaking how the technique works.

Came from Steve Mould. Subbed but this could get confusing what with being a big Alec Steele fan

Idea: Get as much data of each patient as possible: has been in contact,? when?, has symptoms?, how severe?. Use neural networks or plain statistics to estimate the chance of that patient of been positive. Test them in groups of size inversely proportional to their chance of been positive. If a big group tests positive subdivide it in smaller groups and test those. Use the results to update the neural networks or statistics. You can also test wastewaters to estimate the baseline chance of a region.

Quite suffisticated method! But still, there is the problem at this stage that we are still trying to build models of the propagation of the virus, so in some sense, the measure for this method is also the target of the method, wich makes it quite conflicting as a solution to the problem. Since the actual ratio of true positives to true negatives is rapidly changing, depending on the times, how would you decide when to change the measure without affecting the theoretic model of propagation?

All of this makes me think of the recent videos on error correcting codes by 3Blue1Brown and Matt Parker. You could pool your tests using the same groups as calculating parity bits in a hamming code, and you could use 6 tests to uniquely identify a single positive in 57 tests

@austinnar4494

3 жыл бұрын

There's also a lot of research on multi-bit error detection/correction that could be used to make this more robust to outlier samples where like 5% are positive.

Tests are done in groups using this method in China.

Great video. Brought here by Steve's tweet. Also China used the pooling test again to test the entire Qingdao city's population within 5 days. www.google.com/amp/s/www.bbc.com/news/amp/world-asia-54504785. Although they only used the simple pooling instead of the fancy multidimensional pools or combinatorics as you mentioned in this video, still cool to see it in real practice. I suppose there is also a careful balance that needs to be struck between multidimensional pooling methods and the risk of human error being made when the testing pools become less and less intuitive as we go up in dimensions.

Steve Mould helped me to reach here thanks to him and hi to you man❤️

Where is the limiting factor in testing at the moment? Is it the lab space and biochemical analysis or is it the swabs and the kits that get sent out to people?

@DrAndrewSteele

3 жыл бұрын

I don't know the details and it probably varies a bit by country, but I think in the UK it's at least partly due to lab capacity-I don't know if you've been listening to More or Less's excellent coverage on this, but the Government's 100,000 test target in April was met by counting swabs that were posted on that day, but many were of course never returned! So that suggests to me that we're not short on swabs…

Unnatural stabilization

So why not? What's the limiting factor elsewhere in the system? Getting the swabs done? Logistics of transporting the materials or samples?

@DrAndrewSteele

3 жыл бұрын

I don't know. There would definitely be some logistical overhead in labs, but the benefit is so enormous that it's surely worth overcoming-it would need to make testing ten times more logistically challenging before you weren't winning!

@anne-sophiej.9584

3 жыл бұрын

@@DrAndrewSteele Do you think that a country (I prefer not to name it out of respect for my flag 🇫🇷) having refused the help of veterinary laboratories at the worst of the crisis is ready for this🙄? The first preprint I found referring to this technique dates from last April. The capacity to test has been one of the arguments put forward almost everywhere to show muscles. A capacity with objectives formulated in figures, presented as the guarantee of a rapid and efficient response to the emergence of clusters. The goal reached (more than one million per week here, including sometimes one week before getting a result and a failure to respond effectively to the emergence of clusters for more than two and a half months), who knows : perhaps we will now be able to ask ourselves the question of the method...with an average positivity rate of 13 now... There's no greater risk of producing false negatives or false positives. We had several months to think about it in a context where the positivity rate was less than 3. A latency that have severely testing our laboratories. I don't know how to answer the question of whether if a combinatorial pooling strategy would have posed greater logistical issues. Nor do I know if the one who affixed the motto "Why make it simple when we can make it complicated?" at the pediment of the entrance to administration schools used to go through his bathroom window to open the door from inside every time he was going home. Thank you Andrew for this uplifting and perfectly substantiated video !

@DrAndrewSteele

3 жыл бұрын

@@anne-sophiej.9584 Thanks! And, er, the UK refused the help of academic biology labs early in the crisis too…I think there may be a lot of similarities…

cheers steve mould

Amazing the simple way the math is explained for it. But unfortunately the testing part of running test in the whole population is the simplest logistic part. Collection, distribution, tracking and contact tracing are the real hard problems to solve. Those are the ones that can't be solved with brute force, more machines, and robots....

It's super interesting. But when talking about testing everyone in the US, number of tests needed aside, don't you make an assumption that corona virus cases are uniformly distributed geographically, or that you're able to mix samples from wider an area of land than is feasible (to be a practically possible strategy)?

This is pooled testing and has been considered by testing services. It's a good idea in theory but your initial description of the PCR test is incomplete. The Covid PCR test I'm familiar with tests each sample for 2 RNA sequences from the virus (one coding for the capsid and one coding for the nuclear code). Along with a test for human DNA (to make sure someone is actually swabbing themselves, a negative control). If someone has a single trace result (just a positive indicator for one of the viral sequences) it will be treated as a positive result and will need to be retested. And people who have had coronavirus are vastly more likely to give one of these false positive results, due to them carried viral fragments within the body at non contagious levels but still enough to be detected by PCR. This would increase the percentage of positive samples which would break the economics of this idea. Also the second reason this won't currently work is that inside of testing centers we are now seeing >12% positivity rates in samples being tested, going back to your graph early in the video this again would break the efficiency of pooled testing. I don't want to be a negative Nancy it's just that I've raised this issue with superiors where I work and this answer I got is worth knowing for people who are interested in this kind of stuff. I wrote this comment while I watched and the point of the economic benefit of testing everyone with pooled testing and releasing us from the cost of lockdown at the end is a very good one. Hopefully this idea gets Infront of someone who can get pooled testing available for very large groups.

@antisocialbob968

3 жыл бұрын

With regards to what you said about traces of dna being in someone who has had the virus. At the University of Cambridge they have told people not to sign up for the asymptomatic testing program if they have had the virus within the last 8 weeks. If there were to be large scale asymptomatic testing this idea would potentially be a solution to that.

maybe thats a lack of my english but we just talk about the laboratory test but everybody gets his own teststick in their nose?^^

I’m going to post this for the governor of North Carolina in the USA on his Facebook!🤯

@pingnick

3 жыл бұрын

His Facebook hahaha along with over 1,000 other comments wow anyway Australia I hope can utilize this to get rid of Covid even in the next few months!?

Great vid, Your audio is veru quite, even at max volume I have trouble hearing you

@DrAndrewSteele

3 жыл бұрын

Thanks for the feedback! I agree, and will normalise to a higher level on future videos…

If we're living in an ideal world of mathematics this strategy will works perfectly. But in the real world things are more complicated. First of all it does not easy to detect COVID-positive pacients even testing them separately. The second, PCR is not that sensitive and precise as one may thinks. The third, by the time you find a positive patient, he could already have transmitted the infection to another person. So in my opinion it's better to stick with self-isolation and wearing masks and leave testing to sick people who shows symptoms.

This was SUCH a great video! Thanks! What a different world it would be if we made decisions based on math and science. But when we have politicians who denounce science and support crazy conspiracy theories, making things better so often hinges more on political struggles than mathematical or scientific thinking. Which makes us scientists very sad and makes us have to reluctantly enter the world of politics if we want to see change. We in the US have a president who said he wanted to 'slow the testing down'. We also barely even have a public health system.. so testing has been done almost exclusively on a clinical basis (do I have it?) rather than on a public health, epidemiological basis. In order to use pooled testing methods, we'd have to invent a public health system in a country who thinks that public health is socialism and therefore evil.

How does test false positive and false negatives rates of the test influence pooling tests rates?

@DrAndrewSteele

3 жыл бұрын

See the FAQ in my pinned comment!