Why didn’t Theranos work? (and could it have ever worked?)

82 views
0

I’ve heard of PCR before (polymerase chain reaction) where more copies of a DNA sample can be rapidly made. If the problem was that the quantity of blood that Theranos uses is too small, why wasn’t PCR used/ (if it was) why didn’t it work?

Also if I’m completely misunderstanding PCR, if someone could for that too, I’d appreciate it, thank you!

In: 148

I don’t think the tests they were planning to run were all based on genetic code, e.g. presence of antibodies in the fluid.

e: [info](https://www.refinery29.com/en-us/2019/03/224904/theranos-edison-machine-blood-test-technology-explained)

PCR amplies nucleotides. Most (All?) of the diseases they wanted to measure are not diagnosible usong this as a analytt. Typicaly one looks for metabolites or proteins.

Even from a basic physics / chemistry point of view, some of what they wanted to do was simply against the laws of science.

Like, these samples they were taking were very small. Sometimes what you’re looking for is a very rare molecule, such trace amounts that the idea that a detectable number of these would be present in such a tiny sample, let alone reliably so, let alone using the same tiny sample for hundreds of such tests…

It’s against the laws of mathematics. Some tests are looking for very small trace amounts of something, so if your sample is very small then you just don’t have enough to find what you’re looking for.

Add to this other practical issues, like often a test will modify the sample, like you add some reagent or catalyst to find what you’re looking for, this modifies the sample. As a result, the ability to use one sample for multiple tests is limited. Often you have to split your sample up for different tests, which makes their tiny sample even more ridiculous.

Like, in chemistry a statistically significant sample size for most things isn’t *that* big in the sense that even a small amount of something is still a crazy large number of molecules. But when you take these tiny samples and necessarily in reality need to then start splitting that into smaller samples for testing, you’re approaching homeopathic quantities of some things.

Not all blood tests are equal.

Most require very little blood, between 5 and 30 ml of blood. Hence vacutainer tubes are standardized.

Pcr only work for certain things BECAUSE they use DNA. They replicate viral or Patient DNA and specific markers are identified to be looked for. Thus by counting the number of markers found you can determine whether a patient has a Virus or genetic affliction.

But other tests do not involve genetic material. Tests such as Full blood count or even just a Hemaglobin test, you are actually measuring a specific thing in the body and it has nothing to do with genetic material.

Now the amount they wanted to use, was microscopic, so you it does not fall within standards of testing, sometimes you need more volume cause you need to rerun to confirm or do another smear manually and drawing again is something patients do not like. So min blood volume for a test, is usually enough to run it twice or enough that if a screening is positive, a confirmation test can also be run.

Source: 8 years in pathology. Ask if I am unclear or you have more Qs

Some of it can work. A fingerprick glucometer or haemoglobin can give you the amount of sugar in your blood or how concentrated your blood is based on a drop of blood. A blood gas machine uses not much more than a drop to give you quite a lot of data. These can have issues because a lot of things can affect the blood and the drop that you get might not be reflective of the rest of the blood in your body because of a variety of reasons. If you’re looking for a certain concentration of something in the blood, it can wildly swing from drop to drop if you only collect a small amount, compared to if you collected like 5mL of it.

The limiting factor was going to be how many tests you can get off a sample. They advertised a lot for a small sample which is never going to be physically possible. But if you only need like one or two sets of tests, we already do that with [babies](https://www.bd.com/assets/images/our-products/blood-and-urine-collection/blood-collection/microtainer-blood-tubes_RC_PAS_BC_0616-0001.png), but the machine used to run it is room-sized.

0 views
0

I’ve heard of PCR before (polymerase chain reaction) where more copies of a DNA sample can be rapidly made. If the problem was that the quantity of blood that Theranos uses is too small, why wasn’t PCR used/ (if it was) why didn’t it work?

Also if I’m completely misunderstanding PCR, if someone could for that too, I’d appreciate it, thank you!

In: 148

I don’t think the tests they were planning to run were all based on genetic code, e.g. presence of antibodies in the fluid.

e: [info](https://www.refinery29.com/en-us/2019/03/224904/theranos-edison-machine-blood-test-technology-explained)

PCR amplies nucleotides. Most (All?) of the diseases they wanted to measure are not diagnosible usong this as a analytt. Typicaly one looks for metabolites or proteins.

Even from a basic physics / chemistry point of view, some of what they wanted to do was simply against the laws of science.

Like, these samples they were taking were very small. Sometimes what you’re looking for is a very rare molecule, such trace amounts that the idea that a detectable number of these would be present in such a tiny sample, let alone reliably so, let alone using the same tiny sample for hundreds of such tests…

It’s against the laws of mathematics. Some tests are looking for very small trace amounts of something, so if your sample is very small then you just don’t have enough to find what you’re looking for.

Add to this other practical issues, like often a test will modify the sample, like you add some reagent or catalyst to find what you’re looking for, this modifies the sample. As a result, the ability to use one sample for multiple tests is limited. Often you have to split your sample up for different tests, which makes their tiny sample even more ridiculous.

Like, in chemistry a statistically significant sample size for most things isn’t *that* big in the sense that even a small amount of something is still a crazy large number of molecules. But when you take these tiny samples and necessarily in reality need to then start splitting that into smaller samples for testing, you’re approaching homeopathic quantities of some things.

Not all blood tests are equal.

Most require very little blood, between 5 and 30 ml of blood. Hence vacutainer tubes are standardized.

Pcr only work for certain things BECAUSE they use DNA. They replicate viral or Patient DNA and specific markers are identified to be looked for. Thus by counting the number of markers found you can determine whether a patient has a Virus or genetic affliction.

But other tests do not involve genetic material. Tests such as Full blood count or even just a Hemaglobin test, you are actually measuring a specific thing in the body and it has nothing to do with genetic material.

Now the amount they wanted to use, was microscopic, so you it does not fall within standards of testing, sometimes you need more volume cause you need to rerun to confirm or do another smear manually and drawing again is something patients do not like. So min blood volume for a test, is usually enough to run it twice or enough that if a screening is positive, a confirmation test can also be run.

Source: 8 years in pathology. Ask if I am unclear or you have more Qs

Some of it can work. A fingerprick glucometer or haemoglobin can give you the amount of sugar in your blood or how concentrated your blood is based on a drop of blood. A blood gas machine uses not much more than a drop to give you quite a lot of data. These can have issues because a lot of things can affect the blood and the drop that you get might not be reflective of the rest of the blood in your body because of a variety of reasons. If you’re looking for a certain concentration of something in the blood, it can wildly swing from drop to drop if you only collect a small amount, compared to if you collected like 5mL of it.

The limiting factor was going to be how many tests you can get off a sample. They advertised a lot for a small sample which is never going to be physically possible. But if you only need like one or two sets of tests, we already do that with [babies](https://www.bd.com/assets/images/our-products/blood-and-urine-collection/blood-collection/microtainer-blood-tubes_RC_PAS_BC_0616-0001.png), but the machine used to run it is room-sized.