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What law of physics makes what Theranos attempted to achieve impossible? They were still drawing blood from the patient. Thus, it seems theoretically possible

What law of physics makes what Theranos attempted to achieve impossible? They were still drawing blood from the patient. Thus, it seems theoretically possible for technology to overcome the challenges the approach presents.

cmdrfred 10y ago
The law of sample sizes? If I ask one person who they are going to vote for I can't tell you who is going to win the election.
pfortuny 10y ago
Concentration is a global property which cannot be assessed locally in a fluid.
- danellis 10y ago
  So all blood tests are useless?
  - dingo_bat 10y ago
    Blood tests use a relatively large amount of blood to counter the problem. Also many blood tests are repeated multiple times before the doctor produces the final diagnosis. So multiple units of blood from a vein distributed over days vs a pinprick's worth of blood from a finger.
    - Noseshine 10y ago
      Also, blood found in a relatively large vein is much closer to the body average than that found in a capillary area, where much of the liquid is from extracellular space and not even coming from within blood vessels. Of course, extracellular space is filled from blood serum, but a lot of stuff has different concentrations in ECF.
jcranmer 10y ago
Quoting from a comment on one of Derek Lowe's posts on the subject (http://blogs.sciencemag.org/pipeline/archives/2015/10/15/theranos-and-its-blood-test-machine http://blogs.sciencemag.org/pipeline/archives/2015/10/15/the...) (note that a large fraction of commenters are active chemistry, medical, or biology researchers): > The blood you get from a prick will be a mixture of blood from small venules, small arterioles, capillaries and lymph vessels, mixed with whatever loose tissue and cells have been cut by the prick and carried over into the blood. No way you could ever get a reliable CBC from such a sample. Since the kind of general blood tests that this company is targeting are usually CBC + chem panel, even if you could get your chem results from the prick, you still need a normal blood draw for the CBC, so the competitive advantage that they are trying to push (quick sampling by patient at pharmacy, without need for phlebotomist) is lost. On top of that, the variability inherent in chem results from prick blood will be significant for several analytes, like CK and AST (present in muscle so could be raised from prick injury), glucose and lipids (different levels in venous or arterial blood or lymph), etc… In short, while it might be possible to reliably use only µL of blood for tests, using µL of blood for dozens of tests seems questionable, and the chosen blood source is likely to be mostly worthless.
- gmarx 10y ago
  You underestimate the magic of machine learning! :0...kidding. Sort of. I suspect they thought there was a software solution to this problem (and for all I know there might be)
  - bllguo 10y ago
    What? Please elaborate! I can't think of how software overcomes this problem.
    - gmarx 10y ago
      I doubt it can but if you did a large number of blood tests with finger stick and a large number at the same time with a regular blood draw you could put that data into some machine learning and see if you could figure out an algorithm to correct the results. You'd probably need more data than just the final counts. Maybe some kind of imaging data? Maybe ions? It's tough to speculate. Machine learning learning is all about finding patterns. Maybe some pattern could be used to do the correction?
Piloti 10y ago
It doesn't exactly violate the laws of physics so much as the laws of variance and statistics. Blood content varies from place to place - and a lot of the fluid sampled in a fingerprick isn't blood anyway. (I'm not an expert on this, but credentialed experts in the topic were skeptical from the start.) The result could be right. But it probably won't be. Let's use an analogy: imagine a tech company said that with their new wondertech, they could do opinion polls where they would only have to poll one person to know who would win the next election or what will happen to the economy. Wow! Magic! Polls would be so much cheaper! Much better forecasting! #Disruption! Except it's impossible. People vary a lot. Opinion polls work - they can only work - by sampling lots of people. If you sample one person in a halfway close election, there's a good chance that you'll pick someone supporting the losing side. In retrospect, what Theranos did was the classic Big Lie approach to false claims: make an extremely unlikely claim that was so shocking that it was hard to imagine that they would just lie so blatantly about the trustworthiness of their technology. I think in retrospect people were stunned into submission and accepting that, hey, maybe they had managed to overcome these problems.

cmdrfred 10y ago

The law of sample sizes? If I ask one person who they are going to vote for I can't tell you who is going to win the election.

pfortuny 10y ago

Concentration is a global property which cannot be assessed locally in a fluid.

danellis 10y ago
So all blood tests are useless?
- dingo_bat 10y ago
  Blood tests use a relatively large amount of blood to counter the problem. Also many blood tests are repeated multiple times before the doctor produces the final diagnosis. So multiple units of blood from a vein distributed over days vs a pinprick's worth of blood from a finger.
  - Noseshine 10y ago
    Also, blood found in a relatively large vein is much closer to the body average than that found in a capillary area, where much of the liquid is from extracellular space and not even coming from within blood vessels. Of course, extracellular space is filled from blood serum, but a lot of stuff has different concentrations in ECF.

jcranmer 10y ago

Quoting from a comment on one of Derek Lowe's posts on the subject (http://blogs.sciencemag.org/pipeline/archives/2015/10/15/theranos-and-its-blood-test-machine http://blogs.sciencemag.org/pipeline/archives/2015/10/15/the...) (note that a large fraction of commenters are active chemistry, medical, or biology researchers): > The blood you get from a prick will be a mixture of blood from small venules, small arterioles, capillaries and lymph vessels, mixed with whatever loose tissue and cells have been cut by the prick and carried over into the blood. No way you could ever get a reliable CBC from such a sample. Since the kind of general blood tests that this company is targeting are usually CBC + chem panel, even if you could get your chem results from the prick, you still need a normal blood draw for the CBC, so the competitive advantage that they are trying to push (quick sampling by patient at pharmacy, without need for phlebotomist) is lost. On top of that, the variability inherent in chem results from prick blood will be significant for several analytes, like CK and AST (present in muscle so could be raised from prick injury), glucose and lipids (different levels in venous or arterial blood or lymph), etc… In short, while it might be possible to reliably use only µL of blood for tests, using µL of blood for dozens of tests seems questionable, and the chosen blood source is likely to be mostly worthless.

gmarx 10y ago
You underestimate the magic of machine learning! :0...kidding. Sort of. I suspect they thought there was a software solution to this problem (and for all I know there might be)
- bllguo 10y ago
  What? Please elaborate! I can't think of how software overcomes this problem.
  - gmarx 10y ago
    I doubt it can but if you did a large number of blood tests with finger stick and a large number at the same time with a regular blood draw you could put that data into some machine learning and see if you could figure out an algorithm to correct the results. You'd probably need more data than just the final counts. Maybe some kind of imaging data? Maybe ions? It's tough to speculate. Machine learning learning is all about finding patterns. Maybe some pattern could be used to do the correction?

Piloti 10y ago

It doesn't exactly violate the laws of physics so much as the laws of variance and statistics. Blood content varies from place to place - and a lot of the fluid sampled in a fingerprick isn't blood anyway. (I'm not an expert on this, but credentialed experts in the topic were skeptical from the start.) The result could be right. But it probably won't be. Let's use an analogy: imagine a tech company said that with their new wondertech, they could do opinion polls where they would only have to poll one person to know who would win the next election or what will happen to the economy. Wow! Magic! Polls would be so much cheaper! Much better forecasting! #Disruption! Except it's impossible. People vary a lot. Opinion polls work - they can only work - by sampling lots of people. If you sample one person in a halfway close election, there's a good chance that you'll pick someone supporting the losing side. In retrospect, what Theranos did was the classic Big Lie approach to false claims: make an extremely unlikely claim that was so shocking that it was hard to imagine that they would just lie so blatantly about the trustworthiness of their technology. I think in retrospect people were stunned into submission and accepting that, hey, maybe they had managed to overcome these problems.