PCR False Positives?

[cabmandone]

From the NYT article they're making an argument that 40 cycles can identify too small of a viral load to the point that the person isn't really sick or able to infect others. One of the people quoted said that people identified as positive at 40 cycles should be contact traced. There were really a few arguments in the NYT piece. One was that more testing needed to be done using rapid tests rather PCR which was tied in to PCR being too sensitive at 40 cycles and too slow in a situation where a virus was spreading rapidly. But saying "85-90% wouldn't have been positive if we used 30 cycles as the threshold" isn't the same as saying "90% of PCR tests were false positive"

Here's a decent read with lots of links about PCR testing cycle thresholds and their importance.
https://www.usatoday.com/story/news/factcheck/2021/02/11/fact-check-post-distorts-whos-covid-19-pcr-testing-guidelines/4340677001/

From the link: " But including CT values is not entirely clear cut. Dr. Matthew Binnicker, a professor of laboratory medicine and pathology at the Mayo Clinic, told FactCheck.org that taking high PCR cycle values, or low-positive PCR results, as indicating someone is no longer infectious may miss someone who has "only recently became infected and has yet to hit peak infectiousness. He also clarified "the quality and type of sample can also affect how many cycles are needed to detect the virus, so it's not always the case that a high-cycle result means a person is harboring remnants or only small amounts of the virus,"

[javadog]

You clowns aren't approaching this from the correct direction. The graphs I posted were from the study I linked. If you read the goddamn thing, it was a relatively small study of people that had the virus, that had the disease and the tests were from different stages in their illnesses. The graph was simply posted to show that there is a steep drop off in the likelihood of finding live virus in tests run more than 24, 25 cycles. By the time you get to 40 cycles, or more, you're dealing with virus fragments that can cause no disease.

Take a look at the first graph. By the time you get to 40 cycles, the probability of live virus being recovered is near zero. For the less than astute observers among you, I should point out that the value of zero on the y axis is above the bottom line of the graph. As stated in the study, the confidence window is fairly large because the number of samples in the study was relatively small (under 200) but note how quickly the confidence window tightens up at high cycle values.

Looking at the second graph, there are no positive cultures for any sample older than about 10 days from the onset of symptoms. None.

The CDC has studied this in the past and they understand it. That's why it made no sense for them to promulgate the idea that 40 cycles was the right number to use. A bunch of people questioned this last year, which gave rise to the study and article I originally read. As more people have figured out that their guidelines were bull****, they have changed them. It wasn't just this aspect of the problem alone; they back-tracked on a number of issues. WHY DID THEY DO THIS?

The question you need to ask is this one:

If you are asymptomatic and take a test, if that test is run through 40 cycles before the fluorescence exceeds background levels, what is the likelihood that you have in your body a sufficient load of live Sars virus to cause the Covid disease? I'm telling you that the answer is essentially none. Zero. I am not interested in a positive test that means that it has found a few dead virus fragments that can't cause any disease. That means nothing.

Don't like my outlook? Go dig a big, deep hole in your backyard and cower in it, until your precious savior Fauci sounds the all-clear alarm.

IDGAF.

[cabmandone]

And still... no support for the 97% false positive claim... from anyone who seems to believe the claim is true in any way. There's a reason the claim of 97% false positives at 40 cycles is hard to support... It's because there is no real support for it.

Stealth edited...

[thor66]

watch out now, jabadog is a noted virologist

[1990C4S]

A bit more info, they have found a positive patient that he did not operate on, but he was exposed to.

The surgery was such that the patient was not wearing a mask.

[cabmandone]

I read something this morning and meant to post it here but I can't find the piece. One of the things the article I read mentioned was that the person could be immunosupressed or immunocompromised and their reaction to the vaccine didn't create the antibodies that someone with a properly functioning immune system would create.

[1990C4S]

Unfortunately we will never know in this instance. He was isolated ten days away from the hospital and on return to work was told the case is considered a closed positive.

[cabmandone]

Originally Posted by 1990C4S

Unfortunately we will never know in this instance. He was isolated ten days away from the hospital and on return to work was told the case is considered a closed positive.

Well that sucks!

[1990C4S]

I honestly think it was a false positive. But I'm disappointed the hospital didn't dig a bit deeper.

[Tobra]

If the false positive rate is 97% at 40 cycles, and the initial recommendation was for at least 40 cycles, what does that mean?

Originally Posted by cstreit

What I read from this is one doctor says it’s wrong and other says it’s right.

So we just need to ask the right doctors to get the answers we want, perfect.

[cabmandone]

Originally Posted by Tobra

If the false positive rate is 97% at 40 cycles, and the initial recommendation was for at least 40 cycles, what does that mean?



So we just need to ask the right doctors to get the answers we want, perfect.

It means the claim of 97% false positive at 40 cycles is completely unsupportable and false.

[javadog]

Originally Posted by cabmando

It means the claim of 97% false positive at 40 cycles is completely unsupportable and false.

OK, prove that assertion.

[cabmandone]

I have... repeatedly. Now prove that without lowering the threshold to 30 that 40 produces 97% false positive. I wish you luck my friend.

[javadog]

Well, since 40 was the threshold number they used, take a look at the graphs I previously posted and consider the possibility that there was a live virus in a test after 40 cycles.

[cabmandone]

I looked at your graphs. It did not indicate 97% false positive.

[javadog]

Originally Posted by cabmando

I looked at your graphs. It did not indicate 97% false positive.

Take another look. What are the odds of detecting live virus at cycle threshold of 40 or greater?

[cabmandone]

I looked again. No support for 97% false positive.

[javadog]

Originally Posted by cabmando

I looked again. No support for 97% false positive.

That wasn’t the question I just asked. The question is simply, what probability exists of finding live virus at a cycle threshold of 40 or greater?

[thor66]

Why not just pay attn. to cabmando? It will save you a lot of work and stress.

All his posts this are correct.

[cabmandone]

And you're not supporting the claim of 97% false positive. Finding 8% of the people at 40 cycles with culturable live virus does nothing to support the ridiculous claim of 97% false positive at 40 cycles. Now as much as I'd love to continue with this, I see no point in it if you aren't able to support your initial claim. We can go off on tangents about cycle thresholds or whatever tangent you'd like but I'm not going to let you off the hook for supporting your initial claim. As I pointed out to Tobra, there is no evidence to support that absurd claim.