I'd like to share with you what I have learned about the RT-PCR test that is being used all over the world to find "cases". Note, case does not mean you have temperature, that you are feeling bad or coughing. When we see the figure "cases" it could be people that were feeling bad or feeling just fine when the test was done. Hence, we have apples and oranges in that number, sick and not sick.
The PCR technique (
it is NOT a test to identify illness) was developed by Dr. Kary Mullis who in 1993 won the
Nobel Prize in Chemistry. The technique allows rapid amplification (making exact copies) of a small stretch of DNA (also RNA). This method was never meant to be used for diagnosing illnesses which I'll explain shortly why.
So, PCR can be thought of as a special coping machine of DNA/RNA. How does it work ?
1) Take a sample from the nose/throat.
2) Put the samples into 3 PCR processes. Each one SET TO COPY ONLY 1 of 3
segments of the complete SARS-CoV2 virus RNA strand. They don't try to ID the whole RNA strand of the virus.
RNA that is not from CoV2 virus will not (theoretically) react (no coping) in this process. So if there were ZERO samples of SARS-CoV2 virus RNA the processes would copy nothing, again theoretically. Result, NEGATIVE.
3) The copying process is controlled by adjustment of the number of cycles of copying that will be done for the test. The parameter is called Ct. The simplest explanation would be along these lines. If we start with X CoV viruses then for Ct = 2 or two cycles of coping we get following happening,
1st cycle = 2 * X copies made
2nd cycle = 2 * (2 * X copies) = 4 *X copies made
Note this is simply 2 raised to the power of Ct or 2^Ct.
So for Ct = 35 we have 2^35*X copies or 34,359,738,368 * X copies of chosen CoV2 RNA segment.
4) During the process each copy made has attached to it a chemical which fluoresces when exposed to some particular light source in the lab equipment.
This is what decides if the test goes POSITIVE or NEGATIVE, presence of emitted light. No light, NEGATIVE. There is light, POSITIVE. So, more virus copies generate more light. Few or no virus RNA copies and we get faint light or no light.
5) The whole problem with this so called "test" is that
we do not know the INITIAL amount (X) of the virus at the start of the test. There could be 1, 112, 1,532, 2,348,371 or ZERO.
We don't know !!! Keep that in mind always because it is a key to this so called "test".
This is crucial to understanding the potential for misuse of this test. There are other things that are a problem but this one issue is the number 1 starting problem.
6) Some other issues with the test,
a) We do not know if the SARS-CoV2 virus RNA is
dead (killed by immune system) or
alive (able to infect others).
Dead will not infect anyone, live ones potentially COULD.
b) We do not know if the 3 target segments of the SARS-CoV2 virus RNA are not also present in some other viruses leading to
copying of something that is not CoV2
c) We do not know if all 3 SARS-CoV2 virus RNA target segments are actually there for each of the X viruses RNA in the sample
d) We do not know if sample was contaminated during taking and transport
e) We do not know if the samples were in the right temperature during transport (crucial issue).
f) We do not know if the caring out of the test procedure was done correctly in the lab
There is more but the bottom line is that with MASS TESTING things will go wrong but we have no clue where and when.
This is getting a bit long so I will just zero in on the central issue of this test, Ct value used. Different lab all over the world used different values. NOTHING in this test is truly standardized as you are not in the lab to check what they are actually doing. If papaya can bring a POSITIVE result .....
Tanzania , well you get what I mean.
Lets assume that the test detects light and goes POSITIVE if virus copies made equals 3,000,000,000. Also assume that a person who gets sick would have on average X=3000 CoV viruses and when fully recovered or asymptomatic 500 or less in the sample when tested.
Here is a spreadsheet showing what happens at different Ct levels and different initial X values of CoV2 viruses in the sample tested.
What do we see ?
1) A sick person
can be identified by using a cycle Ct value of 20 or higher. Lower Ct the light level would be too low.
2) A person who has recovered from the illness or is asymptomatic would need the test to be set at
23 or higher for the test to say Positive as the initial number of virus is much smaller. So more copies are needed to reach the minimum of 3,000,000,000.
3) A person with very little of the virus would need to have the cycle level
set even higher to get to the detection level needed to set the test to Positive.
From the above you should get the sense of how the test reacts depending on the Ct value and the initial X value of CoV2 virus.
Remember: We never know what that INITIAL X value is. No easy way to do it.
So what happens in the labs ? They just set the Ct value and run it all on automatic. The commonly used value of Ct is/was 36 to 40. Many experts who were not frequent guests on CNN/BBC warned that the value is set too high and would result in people with next to nothing for the Initial value of X in their sample to be identified as POSITIVE CASE. No one listened.
So what you were/are observing are people with NO SYMPTOMS testing POSITIVE which could mean that,
1) the person encountered the virus in tiny amount
2) the immune system defeated it without the person getting sick
3) the healthy person carries the residual RNA of the virus in tiny amounts and setting off the test POSITIVE
because they are using such high Ct.
This is the central problem with this test. Too high Ct combined with continuous testing will result in finding more POSITIVE cases as long as you test and the person was in contact with the virus in low viral load environment or a high one. The test can not answer this question. They have no clu how much virus is in the sample to decide if the person is potential spreader or not. Add to this points a), b) and c) and you know how good this test is !!!
Virology experts I encountered in the Internet (not on CNN/BBC) say the test Ct value should be rolled back to around 26 or a bit lower so as not to pickup people who are not a danger.
So next time you hear "The Positive Cases for today was ...." JUST SMILE !!!!
That's the basics of the controversy around the test RT-PCR. Add to that that there is no Standard test and Standard procedure and you have a Circus where every lab potentially is cooking the soup differently.
m.cnnindonesia.com
news.bloomberglaw.com
www.fiercebiotech.com
abcnews.go.com
