Theranos's whole product concept was unscientific and far more than just an unsolved engineering problem. It is biologically impossible to get accurate results on most assays from a single finger prick drop of blood. That can work reasonably well for a few things like glucose level or positive/negative on antibodies but generally it's a dead end.

You need to add "with the current technology" at the end, and the statement will be accurate.

You can't know what a research will bring, maybe it will be discovered that you can do all these tests through some proxy measurement etc. In biology they don't deal with "laws of nature" in the same sense with the physicist, therefore everything is engineering problem since you always have the option to go above or below the biological processes.

You can't transplant a heart until you find a way to do it, you can't change genes until you find a way to do it.

There's no natural law prohibiting measuring something something from the finger that can be measured from somewhere else, it simply cannot be done with the current methods due to some process going on in the human body. The task would be to find a way around the mechanism that is preventing you doing it.

You have misunderstood the basic biology. This is not a technology issue. For most blood assays the necessary analytes are simply not present in a single finger prick drop of blood at levels that consistently correlate with venous levels. This is pretty much a law of nature and no amount of engineering or research will alter that reality.

Sounds like an engineering issue. I doubt that it's random, therefore other signals could be used to estimate at good enough accuracy. Maybe combining it with saliva or urine samples or finding a correlation with the existence or levels other chemicals etc. can give it away.

You seem to be doubling down on aggressive ignorance of human physiology. You can believe what you like but what you're proposing is simply nonsense in the general case, more akin to alchemy than anything resembling actual science or engineering.

I'm not proposing anything since we talk "in principle", not about anything specific. What I say is that the current technology is not final and anything could be possible and it is an engineering problem unless it's restrained by the fundamental laws of physics. Could be hard or impossible with the current state of the art but that's why we do research and development, aren't we?

"single finger prick drop of blood at levels that consistently correlate with venous levels" is definitely not one of the fundamental laws of nature. They may not correlate but maybe it's possible to acquire the information about the body through some other channels. It's not like there's a single way of surveying the body, right? A specific test can be impossible but another method can be develop for obtaining the same information.

What you are proposing is like trying to calculate the current weather in New York based on cloud cover in Detroit. Sure you can probably find some small statistical correlation but the results won't be useful to a New Yorker trying to plan her day.

If a doctor needs the patient's current platelet count for treatment they're not going to be able to get it through a nasal swab or urine test or whatever. This is restrained by fundamental physical laws. If you're still not getting it then all I can suggest is taking a remedial biology course.

In which case, it wouldn't be done through a drop of blood, as Theranos advertised. It will be done through those undiscovered "magical" means (in the sufficiently advanced levels of technology are akin to magic manner of speaking) that currently elude our understanding both technical and theoretical.

It doesn't matter how it's done. When they promise a drop of blood, what they promise is not drop of blood but a value associated with being able to do these test from drop of blood. If similar value can be delivered through other means, it would be fine. Not drop of a blood but saliva and breathing analysis? Just as good.

Blood test nerds can be disappointed, of course. I doubt that the core audience are the blood test aficionado, but you can always make them happy by saying "We are confident that the test can be done through single drop of blood in 2 years".