PCR Tests?

[knownunknown]

Just listened to a Lex Fridman podcast whose guest was Michael Mina(Harvard professor doing research on infectious disease and immunology).

He's making the case that the PCR tests are beyond useless(actually a hinderance) in an pandemic and we should move to a different kind of test, rapid at home testing.(Paper strip test in which you swab the front of your nose, put it into a tube with liquid and it works like a pregnancy test, one line you're positive, two lines you're negative.) It answers one simple question, "Am I infectious?"

He says the PCR test should be reserved for diagnostics but don't do a lot about severing chains of tranmission. Also the fact that there is no delay in the result can have a massive effect on transmission.

He says that PCR test are far too sensitive, someone who has covid is usually only infectious for a few days, but the PCR test will trigger for a few months after you've had covid. He says the rapid at home test will give instant results, and will only trigger if that person is infectious at that particular time. He also says that governments are catching on finally, so maybe we will see a change of strategy here soon.

Maybe he's making these tests sound far better than they are... if not why have we not implemented these tests already?

From the HSE website " PCR testing is the most reliable way of diagnosing COVID-19. It is the main type of test that we use."

[Peregrinus]

Well, it's worth noting that there is no contradiction at all between what is on the HSE website ("PCR test is the most reliable") and what Prof. Mina said in the podcast. It may be that the paper strip test does detect when you are actually infectious, but with a relatively high rate of false negatives/false positives, whereas the PCR test detects whether you have been infected - a different question - with a high degree of reliability. So it's not a simple case of one of these tests being better than the other; all tests will have relative strengths and weaknesses, and you'll want to balance these off against one another in the context of the purpose(s) for which you are doing the tests.

In fact Mina makes this point - PCR is good for diagnostics; paper strip may be better for severing chains of transmission (although I note that you don't report him as saying that it is better for that purpose; he just says that PCR isn't very good for that purpose).

I didn't hear the podcast, obviously, but I'm puzzled by the claim that the PCR test is not good for severing chains of transmission. While it may detect people who aren't infectious and so impose unnecessary restrictions on them, from what you say it should reliably detect everyone who is, or may become, infectious. And that's all you need if severing chains of transmission is your only or main object. Whereas if the paper strip test only pings if you are actually currently infectious, then it will miss people who have been exposed and are infected but are not yet infectious, and that looks like a fairly major flaw, so far as interrupting transmission goes.

Still, I didn't hear the podcast, and of course I haven't seen any of the information that underlies the podcast. It may be that the paper strip test is on balance more apt for transmission control; it's just that this isn't a simple question with a one-word answer, and some of the material you report as being in the podcast suggests that there may be some trade-offs involved in using it, in which case we need to identify those and be satisfied that there are good trade-offs to make.

Maybe we will see a change of strategy soon. But, no matter when the strategy is changed, the question you pose ("why wasn't it changed sooner?") can always be asked. This is a novel disease, with novel diagnostic and therapeutic protocols. Knowledge is advancing rapidly, and we should expect diagnostic, treatment and infection control mechanisms to be changing more than once as this happens. When they do change, this doesn't mean that the earlier decisions now being supplanted were wrongly made at the time, or that the change should have been made sooner than it was.

[CelticRambler]

The different tests have a greater or lesser importance according to how prevalent the virus is, how serious is the illness, and how the results will be used to implement control measures. The testing arrangements over the course of this pandemic have been carried out in a way that makes them next to useless for proper disease control, because the people laying down the rules are politicians, not doctors; and the people being tested are more concerned about personal "liberty" than communal health.*

So it doesn't matter whether you use a highly specific "gold standard" PCR test or a quick-and-easy "good enough" spit test, the result will be the same - loads of inaccurate and/or no-longer-relevant results that do nothing to help control the spread of the disease, mainly because the population being tested is not being subject to the necessary movement restrictions and on-going surveillance needed to effect such control (except in China). This is why, in the what-if exercise I was involved in a few years ago, it was concluded that we would suffer precisely the situation that has become so familiar to all of us over the last two years.

* Somewhat ironically, while it is frequently asserted that the measures needed for control of this infection would cause/have caused enormous economic damage, where there is a very real risk of damage to our agricultural economies, the control measures are considerably more draconian - but we're happy to implement them week after week, year after year. Not a peep out of anyone about the (in)competence of "experts" or infringements of animal rights. Those controls are almost exclusively rely on PCR tests.

[490808]

If everyone could do a cheap at home test how on earth would the scientists know if there was yet another mutation to an even more virulent form?

[knownunknown]

So it doesn't matter whether you use a highly specific "gold standard" PCR test or a quick-and-easy "good enough" spit test, the result will be the same - loads of inaccurate and/or no-longer-relevant results that do nothing to help control the spread of the disease, mainly because the population being tested is not being subject to the necessary movement restrictions and on-going surveillance needed to effect such control (except in China). This is why, in the what-if exercise I was involved in a few years ago, it was concluded that we would suffer precisely the situation that has become so familiar to all of us over the last two years.

In the podcast he says that we could use these spit tests to isolate ourselves. This would lead to better results as far as transmission is concerned. To be fair he also says we should be testing waste water and other such signs of community level transmission, then to use the spit tests in areas already identified as high risk. If we knew we were infectious, actually infectious, probably most of us would stay home, without the need for any on-going surveillance, at least is the argument that Mina makes. Of course there will always be a few that don't comply and don't seem to care about others; but we only need r<1 for transmission to stop. If 100 people infect only 99 others then happy days.

I can't paraphrase what he's saying nearly as well as he actually says it; and actually I made it into a false dichotomy. He doesn't say to stop using the PCR tests, just that they should be used for diagnostics and not for the 'public health' reasons they are currently used for. For this reason the antigen spit test would be far better.

Anyone have reasons to disagree here? My only one is that he held up the UK as an example of how well the antigen tests could be used; but they don't seem to be faring so well.

[490808]

As reference has been made to the UK I'll point out that DIY antigen tests are free over there. You can pick boxes of 7 up from any chemist. Max two boxes at a time. Might be useful info for anyone travelling to the UK

[Hairy-Joe]

Personally I think self administered antigen tests are a waste of time. There'll be a large portion of people who will either accidentally or on purpose not take the sample correctly. Having had two PCR tests, getting the swab taken is most uncomfortable and that stick goes WAY up the nose. Personally I would have great trouble shoving the swab stick up that far. I imagine other people would have the same difficulty. Result, an incomplete sample.

A false negative result is the worst thing that can happen

[knownunknown]

Personally I think self administered antigen tests are a waste of time. There'll be a large portion of people who will either accidentally or on purpose not take the sample correctly. Having had two PCR tests, getting the swab taken is most uncomfortable and that stick goes WAY up the nose. Personally I would have great trouble shoving the swab stick up that far. I imagine other people would have the same difficulty. Result, an incomplete sample.

A false negative result is the worst thing that can happen

This was mentioned in the podcast, the antigen test you just brush the front of your nose, you're not instructed to penetrate the brain like the PCR ones. I haven't taken one though, I'm sure someone that has could confirm.

[CelticRambler]

he says that we could use these spit tests to isolate ourselves. ... he also says we should be testing waste water ... If we knew we were infectious, actually infectious, probably most of us would stay home ... Of course there will always be a few that don't comply ...

All that coulda-shoulda-woulda is why a strategy such as this is doomed to failure. You cannot control a disease if you don't have control, and if you're counting on people who cannot even wear a face-mask correctly (never with dealing with those who actively undermine the public health authority's best efforts because freeeeedom! or whatever) then you don't have control.

These quick-and-easy tests are not like a pregnancy test. In that case the person taking the test (usually) wants to know if they are pregnant, so those most at risk of being pregnant will take care to ensure that they do the test correctly and use the (positive) result to define a particular course of action. There is, unfortunately, a wealth of evidence to show that people with a suspected or confirmed contagious disease will take steps to avoid being subject to whatever measures are required to limit its spread.

Testing is of no use unless there is a sound, coherent plan of action behind it, one that is applied and enforced without exception. There wasn't one at the beginning of this pandemic, when the disease was known about in China but hadn't been detected in Europe; there wasn't one afterwards, when we knew the virus had arrived here; there still wasn't one when it was spreading like wildfire; and there's still no coherent policy in place anywhere ... except China.

[Abella]

You do know a PCR test cant distinguish that you are infected with Covid-19 or any other types of flu or covid strains. its worthless in the way its currently used

[Hairy-Joe]

You do know a PCR test cant distinguish that you are infected with Covid-19 or any other types of flu or covid strains. its worthless in the way its currently used

Ah no you're wrong on that. PCR looks specific genetic material. That's how it distinguishes between the different viruses.

We use PCR at work to ID things all the time

[knownunknown]

Well it seems we do have state issued antigen tests as of last week. RTE reported that antigen tests are now sent out to close contacts of confirmed cases. Maybe not everyone will use them properly, but many will now have the chance to visit their elderly relatives with a bit more confidence. Let's hope they can help to reduce the transmissibility.

[Abella]

Ah no you're wrong on that. PCR looks specific genetic material. That's how it distinguishes between the different viruses.

We use PCR at work to ID things all the time

PCR test cant show you have a certain strain of covid, thats a fact, not disputed by anyone, other than yourself. They take a positive PCR test and then send it for a special type of testing called genomic sequencing.

https://fullfact.org/health/delta-variant-tests/
https://www.health.com/condition/infect ... ta-variant
https://fortune.com/2021/06/30/covid-de ... detection/


So is there a test for the Delta variant?
This is where things get a little tricky. Technically, there is a test for the Delta variant—but it's not something you or your doctor has access to. "There is no commercial test for the Delta variant," Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, tells Health. Instead, what happens is that a "selected sample" of positive polymerase chain reaction (PCR) tests are "further studied to look for the characteristic mutations of the Delta variant," Dr. Adalja explains.

Texas Department of State Health Services FAQ: “How can I tell if I have the Delta variant? Do labs report that to the state? That information may not be readily available. The [PCR] viral tests that are used to determine if a person has COVID-19 are not designed to tell you what variant is causing the infection. Detecting the Delta variant, or other variants, requires a special type of testing called genomic sequencing. Due to the volume of COVID-19 cases, sequencing is not performed on all viral samples. However, because the Delta variant now accounts for the majority of COVID-19 cases in the United States, there is a strong likelihood that a positive test result indicates infection with the Delta variant.”

[490808]

In the UK they seem to have far more of a handle on the variants. If you do a positive antigen test then you are supposed to also take a PCR test so that new and current strains can be checked. This article suggests that in the UK they have done a over million tests so far to check what the current variants are https://www.bbc.com/news/health-58965650

[Hairy-Joe]

PCR test cant show you have a certain strain of covid, thats a fact, not disputed by anyone, other than yourself. They take a positive PCR test and then send it for a special type of testing called genomic sequencing.

https://fullfact.org/health/delta-variant-tests/
https://www.health.com/condition/infect ... ta-variant
https://fortune.com/2021/06/30/covid-de ... detection/


So is there a test for the Delta variant?
This is where things get a little tricky. Technically, there is a test for the Delta variant—but it's not something you or your doctor has access to. "There is no commercial test for the Delta variant," Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, tells Health. Instead, what happens is that a "selected sample" of positive polymerase chain reaction (PCR) tests are "further studied to look for the characteristic mutations of the Delta variant," Dr. Adalja explains.

Texas Department of State Health Services FAQ: “How can I tell if I have the Delta variant? Do labs report that to the state? That information may not be readily available. The [PCR] viral tests that are used to determine if a person has COVID-19 are not designed to tell you what variant is causing the infection. Detecting the Delta variant, or other variants, requires a special type of testing called genomic sequencing. Due to the volume of COVID-19 cases, sequencing is not performed on all viral samples. However, because the Delta variant now accounts for the majority of COVID-19 cases in the United States, there is a strong likelihood that a positive test result indicates infection with the Delta variant.”

But you said that PCR couldn't distinguish between Covid and any other flu. So now you are changing it to any types of Covid. Which is it?

Edit, and of course I know PCR can't distinguish between different Covid strains. That's why genomic sequencing is required.

[Abella]

But you said that PCR couldn't distinguish between Covid and any other flu. So now you are changing it to any types of Covid. Which is it?

Edit, and of course I know PCR can't distinguish between different Covid strains. That's why genomic sequencing is required.

COrona Virus I.D 2019 shortened to COVID-19, it was the corona virus strain first identified in 2019
You would never guess but the corona virus has been with us for a long time, you can check it out they was a Covid12, a Covid15, a Covid10 and so on it goes, the PCR test cant tell the difference between Covid19 original strain and the delta variant, it also cant tel the difference between Covid19 and Covid09 or any other Coronavirus from another year.
So all these PCR tests are really unsuited at what they are been currently used for and we wont even get into the +40 cycles they run them at, the inventor of the test has stated its worthless at high cycles .

[PureIsle]

Maybe I have this wrong, but I think that the PCR test searches for something in a sample which has a specific genomic sequence.
If it finds it then the sample is positive for Sars-Cov2.

My present interest is in how that specific sequence is determined.

I have failed to find any published papers about some entity isolating and purifying a virus from a human sample.

If (ok, a big IF) that has not been done (as some claim) then I am unsure how the specific Sars-Cov2 virus can be determined to be in any sample tested by PCR.

So I went looking for a published paper which stated the virus had been isolated and purified, but found none.
I found lots of videos like the one below, which claim it has never been done.

Can anyone help me out with this?
A link to a published paper in a reputable medical journal which details both 'isolation' and 'purification' of the Covid virus from a human sample would be very useful, thanks.

Example video (one of many) claiming it has not been done:

https://odysee.com/@thisweekinfascism:3 ... on-Fraud:2