Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
- GuyGadeboisTheBack
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
Why would Bozo have suddenly, miraculously, an answer to a question? You dream, Totophe!
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
Obamot wrote:Christophe wrote:The USA stops the use of PCR on 31/12/21!
https://www.cdc.gov/csels/dls/locs/2021 ... ing_1.html
Obamot is going to be happy!
It does not take pride in it, it stinks of dollars on all sides, it was enough to coir where the wind was blowing. And “inventor” Kary Mullis of the PCR test (1985 patent) himself said it was inappropriate!
But it is indeed the inevitable outcome of what I have been announcing from the start (and which has been consolidated over time).
There the “funny ones” are very very bad (it remains across the throat in view of the millions of co-lateral victims ...)
the answer can be found in a copy paste on google translation, which Guitounet has surely done but is careful not to give the result. It says
In view of this change, the CDC recommends that clinical labs and testing sites that used the CDC 2019-nCoV RT-PCR test select and begin their transition to another FDA-cleared COVID-19 test. The CDC encourages laboratories to consider adopting a multiplexed method that can facilitate the detection and differentiation of SARS-CoV-2 and influenza viruses. Such tests can make it easier to continue testing for influenza and SARS-CoV-2 and can save time and resources as influenza season approaches.
it is not the principle of PCR tests that the USA is abandoning, it is the test currently used, to replace it by one that tests both influenza and covid, to have a faster diagnosis of both.
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To pass for an idiot in the eyes of a fool is a gourmet pleasure. (Georges COURTELINE)
Mééé denies nui went to parties with 200 people and was not even sick moiiiiiii (Guignol des bois)
Mééé denies nui went to parties with 200 people and was not even sick moiiiiiii (Guignol des bois)
- GuyGadeboisTheBack
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
ABC2019 wrote:it is not the principle of PCR tests that the USA is abandoning, it is the test currently used, to replace it by one that tests both influenza and covid, to have a faster diagnosis of both.
But that guy is stupid ...
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
GuyGadeboisLeRetour wrote:But that guy is stupid ...
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To pass for an idiot in the eyes of a fool is a gourmet pleasure. (Georges COURTELINE)
Mééé denies nui went to parties with 200 people and was not even sick moiiiiiii (Guignol des bois)
Mééé denies nui went to parties with 200 people and was not even sick moiiiiiii (Guignol des bois)
- Obamot
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
If so, it is even more serious, so there is a good pretext! And statistically it's completely stupid to change the test method (which will continue AT LEAST until 2023 ...) It is therefore a good way to further muddy the waters and deprive researchers of the means to comparison ... And finally the best for the end: why test both simultaneously since the flu is no longer there (hop lãaaaa) what does that mean, that it would not have disappeared !? Ah ... or so “we would have been lied to ”?ABC2019 wrote:it is not the principle of PCR tests that the USA is abandoning, it is the test currently used, to replace it by one that tests both influenza and covid, to have a faster diagnosis of both.
Poor ABC, you suck strawberries already, you should stop thanks.
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
Well, as I visited the lab last week, I took the opportunity to ask questions about the famous PCR test to the head biologist of the lab.
How it works (do you ever know ... it can be used again):
Roughly speaking, the machine identifies a DNA fragment in the sample, in which there is the best chance of finding sequences specific to sars-cov-2. Then, the machine will duplicate this sequence X times (amplification cycle), until a probe detects it. At this time, the test stops.
Then, we look at how many cycles have been done. The reading of the test is therefore above all the number of cycles, rather than the positivity: if we do 200 cycles, we will necessarily have a positivity.
The analysis of the test is therefore made according to threshold values (which I did not retain, sorry). Below X cycles, it is an almost certain positive. Between X and Y, we speak of suspicion (often, we ask for a medical opinion if necessary, for example for a patient already hospitalized). Beyond Y, we consider the test invalid (I'm schematizing, it's a little more complicated than that in real life, but you get the idea)
These cut-off values are established with certain positive samples and certain negative samples (basically, we calibrate to find the right confidence intervals).
Regularly, the lab carries out these verifications: we test some negatives or some positives, to verify the calibration of the machine.
According to the head of the lab, the reliability is greater than 99% in the intervals below X and above Y, and of the order of 90% between X and Y. The test result must therefore be completed by medical examination. (figures for our lab)
Also, it sometimes happens that the machine starts to emit 100% positive tests (this happened once with us), a sign that the machine itself is contaminated. A factory cleaning is then carried out, and all the positive tests are taken again to retest them.
Regarding the change of device: today, many labs use an automatic device that performs a single test, in 15 minutes. It is long, expensive, not interesting for the technician and in addition the machines are not too made for that, they are therefore used very, very quickly. Most labs are therefore looking for PLCs that can be used to:
- more sars-cov-2 tests at a time
-sars-cov-2 tests at the same time as something else, to avoid locking a machine on a single type of test
So much for the technical aspect.
For statistics, we know very well how to change the method along the way, as long as we know the reliability of the data before (with confidence intervals, etc.) and after. Then you have to pay attention to historical comparisons, but with rigor it is done very well.
It is not at all surprising that we are trying to improve the quality and fluidity of the tests, on the contrary, I would say that it took a very long time to come!
How it works (do you ever know ... it can be used again):
Roughly speaking, the machine identifies a DNA fragment in the sample, in which there is the best chance of finding sequences specific to sars-cov-2. Then, the machine will duplicate this sequence X times (amplification cycle), until a probe detects it. At this time, the test stops.
Then, we look at how many cycles have been done. The reading of the test is therefore above all the number of cycles, rather than the positivity: if we do 200 cycles, we will necessarily have a positivity.
The analysis of the test is therefore made according to threshold values (which I did not retain, sorry). Below X cycles, it is an almost certain positive. Between X and Y, we speak of suspicion (often, we ask for a medical opinion if necessary, for example for a patient already hospitalized). Beyond Y, we consider the test invalid (I'm schematizing, it's a little more complicated than that in real life, but you get the idea)
These cut-off values are established with certain positive samples and certain negative samples (basically, we calibrate to find the right confidence intervals).
Regularly, the lab carries out these verifications: we test some negatives or some positives, to verify the calibration of the machine.
According to the head of the lab, the reliability is greater than 99% in the intervals below X and above Y, and of the order of 90% between X and Y. The test result must therefore be completed by medical examination. (figures for our lab)
Also, it sometimes happens that the machine starts to emit 100% positive tests (this happened once with us), a sign that the machine itself is contaminated. A factory cleaning is then carried out, and all the positive tests are taken again to retest them.
Regarding the change of device: today, many labs use an automatic device that performs a single test, in 15 minutes. It is long, expensive, not interesting for the technician and in addition the machines are not too made for that, they are therefore used very, very quickly. Most labs are therefore looking for PLCs that can be used to:
- more sars-cov-2 tests at a time
-sars-cov-2 tests at the same time as something else, to avoid locking a machine on a single type of test
So much for the technical aspect.
For statistics, we know very well how to change the method along the way, as long as we know the reliability of the data before (with confidence intervals, etc.) and after. Then you have to pay attention to historical comparisons, but with rigor it is done very well.
It is not at all surprising that we are trying to improve the quality and fluidity of the tests, on the contrary, I would say that it took a very long time to come!
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
Oh yes, Father Pagès is well informed at least as much as Father Guy, Father Janic or even Father Obamo
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
izentrop »02 / 08 / 21, 12: 25
you mostly forget yourself!Oh yes, Father Pagès is well informed at least as much as Father Guy, Father Janic or even Father Obamo
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"We make science with facts, like making a house with stones: but an accumulation of facts is no more a science than a pile of stones is a house" Henri Poincaré
- Obamot
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
What I mainly know is that the staff are paid with a slingshot and have no idea (most of the time) how or at what threshold the machine is set. Proof of this is, moreover, the passage which contradicts that in the program “Infrarouge” (but a specialist was there to say so), because the Centers (often managed by private labs) which test en masse, are encouraged to find positive tests since doctors see their income increase significantly if their patient is “covid positive” (in addition, this will make them anxious and more susceptible to other pathologies ...). So the unscrupulous doctor quickly understood which lab he had to go to to earn more ... And then there is not only the value “CT” (amplification) there is the reagent used as well as other thresholds. And for a year the CT value was simply not mentioned in the results (it has changed a bit since then).izentrop wrote:Oh yes, Father Pagès is well informed at least as much as Father Guy, Father Janic or even Father Obamo
It is only in clinics with “real” patients with symptoms that they pay attention to the results. That's why last year you saw me refer almost exclusively to hospital lethality stats!
While you have not stopped racing who had the BIGGEST (exponential contaminations curve).
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- Obamot
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Re: Understanding the covid test (serological, pcr, antigenic) of Sars-Cov2 (and its variants)
Yes, it's very incomplete but impossible to cover everything during a simple visit, I admit it ... For example at the start of an epidemic outbreak, there is still little viral material in the samples, so the labs are growing. the amplification in the very settings of the machines, the operators do not know (since the machine works almost by itself, the responsibility lies with the head of the lab), and these facts are not known to the general public or even to zeticians. There can also be a bad selectivity which pushes to do that, where when one has to do with a mutant and the machine reacts less well, then the machine is set differently to achieve “standard result to be achieved closest to the standards”Is not a complete success because it can explode false positives or negatives and it goes almost unnoticed ... We often present the irreproachable side, but how to validate everything in detail and with care, when a country like the France does nearly a million PCR tests per day ... (at the peak of periods) ...Rajqawee wrote:Well, since I visited the lab last week,
Last edited by Obamot the 02 / 08 / 21, 13: 58, 1 edited once.
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