That's a Serological test and it only goes positive about 5 days from infection, by which time you're probably not that contagious. This is a nucleic acid test which directly detects the virus and will be positive if you're contagious. They're complementary, but you need a molecular test to stop the spread. This will be a very good product.
I have no idea if the GenViro test is real/functional, but it does not claim to be a serological test. Nor is it PCR. It claims to harvest monoclonal antibodies from rats challenged with the virus, and then attaches those antibodies to the surface of an electrode in such a way that when the antibodies bind to the virus they change the electrical properties of the electrode.
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).
> 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).
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.
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.
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.
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.
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.
It still relies on a population of antibodies for detection. By the time you’ve built a good population of antibodies to trigger the test you will have been contagious for many days. This test is still very valuable though as confirmation of who has antibodies and is likely immune.
The parent is saying that the antibodies used come from an external source, not from the patient. If what the parent is saying is true, why would the patient need antibodies?
That’s not how the contagiousness works. Most reports have average of 5 days from infection to symptoms, but many people are asymptomatic or have mild symptoms. At least one study says viral shedding is close to peak the day before symptoms and the time course of shedding goes down over time. Saying you are probably not contagious just 5 days after infection is misinformation, especially since incubation can range from 2 to 14 days.
I am not an expert, but it clearly states in the link at the bottom it’s not a serology test, although they do offer a serology test strip with the meter too.
I have also read that it takes between 7 and 14 days from infection until you start to show symptoms. From your comment that would mean that anyone showing symptoms is "probably not that contagious". Given the exclusion rules rules here in the UK that doesn't sound right. What piece is missing?
The onset of symptoms starts between 2 and 14 days after infection with 3 to 6 days being the average depending on the cohort. [1] Outliers exist, such as one patient that did not show symptoms for 27 days. It is unknown when a person becomes infectious, but so far data suggests that its days before symptoms appear for most patients and as many as two thirds may be completely asymptomatic.
People show symptoms at 3 to 13 days. So, if the test is useful at 5+ days, then is should be fine for many/most sick people seeking treatment. Though yes, it would be very limited for prophylactic testing, as in testing all family/close contacts of a known infected person to see who might have caught the disease themselves.
