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by mbreese 2274 days ago
That’s the opposite of what you’d want to do. You want to attach the antigen to a test and screen your body for immune cells with an antibody to the antigen. If you’re actively fighting the virus, you might see enough antigen to show a positive test. But that’s pretty iffy — especially if you’re trying to do this with a finger stick. There just isn’t enough blood to work with for most tests (see Theranos). The PCR tests require nasal or throat samples because that’s where the virus is most abundant (and accessible).
1 comments
jessriedel 2274 days ago
> That’s the opposite of what you’d want to do. You want to attach the antigen to a test and screen your body for immune cells with an antibody to the antigen

No, that's a serological antibody test. They are useful, but they only work once your body has already mounted a response to the virus.

In contrast, PCR tests looks for the actual viral RNA, and they work regardless of what your immune system is doing. In principle, the test I described could do likewise: it identifies the actual virus particles in the same way the (mouse) immune system does: by keying into them with antibodies which in turn trigger a larger response (the voltage).

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mbreese 2274 days ago
Yeah, I get how it works but I can’t see how using a IgG probe to look for antigen would be very accurate. This is particularly true when talking about the amount of blood you get from a finger stick. The data coming out of Theranos should have made this clear.

Unless they are somehow using a glucose meter to monitor more blood than a finger stick?

I’m not doubting that you could have a test that worked by scanning for Coronavirus antigen in blood. But not with the device described here. But even assuming it worked, I don’t see how it would be better than an RNA amplification test.

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jessriedel 2274 days ago
I know nothing about the biology, but I don't think the fact that a fraudulent company failed at a very difficult scientific problem is much evidence.
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mbreese 2274 days ago
The fundamental problem Theranos failed at overcoming was that you can’t accurately measure many things using small volumes of blood. All of the fraud was aimed at covering that up. (Glucose concentration is one of the few tests that does work with low volumes.) The CoV test we’re talking about has the same fundamental issue — you can’t have an accurate test for an antigen using a small amount of blood.

It’s less of a biological problem and more of a statistical sampling problem. The chances of there being a CoV antigen in the small drop of blood that you’d measure with a glucose monitor is very small. Sure, it might work, and the theory behind the device is sound. However, if you had a negative test, you’d never know if it was because you didn’t have CoV or if you just didn’t have any in that small blood sample.

I’d be happy to be wrong about this. A quick blood check as opposed to a 15min (the Abbott test) or 24hr (to 1 week with this backlog) wait would be amazing. But the amount of validation you’d need to demonstrate effectiveness would be equally amazing.

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jessriedel 2274 days ago
As you allude to, that's an argument based on the basic biology and statistics, not based on Theranos. You could have made that argument pre-Theranos. That Theranos tried, failed, and the covered it up is not much new evidence. Lots of companies try and fail on hard problems all the time.

Given that the above test is some random marketing PDF and I haven't heard anyone respectable talk about this mechanism, I don't have much faith in it, so that is consistent with your analysis.

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neuro 2274 days ago
It doesn’t appear that’s the case

https://www.amazon.com/GenUltimate-Blood-Glucose-Strips-Mete...

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jessriedel 2273 days ago
I was referring to Theranos, not GenUltimate.
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jon_richards 2274 days ago
The point is that it’s biologically impossible to test for some things with a finger prick. Theranos was like an electronics company claiming to have “solved” the uncertainty principle. In all these tests people are proposing, you still have to abide by the biological requirements.
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jessriedel 2273 days ago
My point still stands regardless of how confident you are in the biological argument: If it's biologically impossible, then you didn't learn anything from the Theranos debacle.
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