4 ms·

These sensors might work well in the lab, but people have been trying various spectroscopy based noninvasive sensing techniques for the better part of 15 years,

These sensors might work well in the lab, but people have been trying various spectroscopy based noninvasive sensing techniques for the better part of 15 years, with limited success. The problem is not that you can get a nicely correlated signal when holding a stationary phone against a stationary well of known concentration, the problem is how does your sensor perform when: 1. You're exercising (sweat getting between the sensor and the skin) 2. You're on vasoconstrictors (smoking or blood pressure medications) 3. You're taking medication that "looks" similar to glucose (in electrochemical sensors that's ~~ibuprofen~~ acetaminophen, but the number of magnetic analogues, especially in the presence of interference, is surely greater) 4. You have low perfusion 5. You're sleeping on/compressing the sensor. This changes how the blood flows, and needs to be accounted for or you'll risk reading a false low value. These are just a handful of the problems that modern CGMs face, and only a few of them have working solutions.

tzs 3y ago
The article is not about a noninvasive sensing technique.
- ijustlovemath 3y ago
  Magnetometers are noninvasive! They don't penetrate the skin
  - adrian_b 3y ago
    That's not how it is used here. The sample liquid containing glucose, e.g. wine or possibly blood (the sample might need to be diluted first with pure water) is put on a gel that has volume changes depending on the amount of glucose. The volume changes are detected magnetically because the gel is coated with a ferromagnetic material. If this were used for blood glucose, the blood would have to be extracted first by traditional means. This does not seem to be the intended use, because the already existing invasive devices are more convenient. The intended use appears to be for testing food using a device that contains the gel and to which you attach the smartphone in order to read the results.
    - ijustlovemath 3y ago
      Yes, I understand how they conducted the experiment! Because this would not be place under the skin, it still constitutes a noninvasive sensing technique
      - deleted 3y ago
        [deleted]
      - refulgentis 3y ago
        Distinction without a difference, your lead comment is a list of common issues for something that is orthogonal to the article. I appreciate it regardless but some humility is in order :) not being strictly on topic is fine, it's still interesting. But I don't think arguing they're the same thing repeatedly down thread is kind.
      - adrian_b 3y ago
        If this were used for blood, it would be invasive, because the blood must be extracted with needles, exactly like in the current kits for measuring blood glucose. The gel holder would substitute the sensitive strips that are used in such glucose measurement kits and the smartphone would replace the electronic reader that displays the results. Nothing would change about the invasiveness of having to pierce the skin with needles, to extract blood. There exist experimental devices for non-invasive measurement of the blood glucose, whose purpose is to avoid the use of piercing needles, but this new glucose sensor has nothing to do with those. This new glucose sensor is for other uses and its advantage is that it no longer needs a special expensive electronic device for reading the sensor output, but a standard smartphone is good enough.
Paul-Craft 3y ago
> 3. You're taking medication that "looks" similar to glucose (in electrochemical sensors that's ibuprofen, but the number of magnetic analogues, especially in the presence of interference, is surely greater) Huh, I never knew this. Does this mean taking ibuprofen can give you an elevated glucose reading on a blood test?
- ijustlovemath 3y ago
  I misspoke, it's actually acetaminophen (I'm always confusing the two!): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5950984/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5950984/ But yes, presence of acetaminophen with a naive electrochemical sensir will cause false high readings, which are VERY dangerous! The latest generation of sensors have fixed this problem, but with any new sensing tech, you need to make sure you're learning from the mistakes of the past. With a new sensing paradigm, you won't necessarily have problems with the same drugs, but knowing that this kind of constructive interference is a potential problem will help you design a more robust system.
  - jfengel 3y ago
    Just a note about false readings. A diabetic with high glucose is deeply uncomfortable, and will suffer long term damage, but is not in immediate peril. The bigger danger is being low, which will lead to unconsciousness, coma, and death. Insulin brings down blood glucose. Getting insulin when not needed can be deadly. (It's a favorite of murder mystery writers.) False highs are more of a risk than false lows. Which means you may need to administer sugar to a diabetic in an emergency. But unless you're a medical professional you will never need to give them insulin.
    - ijustlovemath 3y ago
      Absolutely, the danger of a false high is that you dose insulin to correct and end up pushing yourself into a dangerous hypoglycemic state. That's why acetaminophen interference is so important to deal with! And while it's true that running a bit high (250-350mg/dL) isn't an immediate risk, DKA is still a possibility once you breach the 300s, and that will land you in the hospital.

tzs 3y ago

The article is not about a noninvasive sensing technique.

ijustlovemath 3y ago
Magnetometers are noninvasive! They don't penetrate the skin
- adrian_b 3y ago
  That's not how it is used here. The sample liquid containing glucose, e.g. wine or possibly blood (the sample might need to be diluted first with pure water) is put on a gel that has volume changes depending on the amount of glucose. The volume changes are detected magnetically because the gel is coated with a ferromagnetic material. If this were used for blood glucose, the blood would have to be extracted first by traditional means. This does not seem to be the intended use, because the already existing invasive devices are more convenient. The intended use appears to be for testing food using a device that contains the gel and to which you attach the smartphone in order to read the results.
  - ijustlovemath 3y ago
    Yes, I understand how they conducted the experiment! Because this would not be place under the skin, it still constitutes a noninvasive sensing technique
    - deleted 3y ago
      [deleted]
    - refulgentis 3y ago
      Distinction without a difference, your lead comment is a list of common issues for something that is orthogonal to the article. I appreciate it regardless but some humility is in order :) not being strictly on topic is fine, it's still interesting. But I don't think arguing they're the same thing repeatedly down thread is kind.
    - adrian_b 3y ago
      If this were used for blood, it would be invasive, because the blood must be extracted with needles, exactly like in the current kits for measuring blood glucose. The gel holder would substitute the sensitive strips that are used in such glucose measurement kits and the smartphone would replace the electronic reader that displays the results. Nothing would change about the invasiveness of having to pierce the skin with needles, to extract blood. There exist experimental devices for non-invasive measurement of the blood glucose, whose purpose is to avoid the use of piercing needles, but this new glucose sensor has nothing to do with those. This new glucose sensor is for other uses and its advantage is that it no longer needs a special expensive electronic device for reading the sensor output, but a standard smartphone is good enough.

Paul-Craft 3y ago

> 3. You're taking medication that "looks" similar to glucose (in electrochemical sensors that's ibuprofen, but the number of magnetic analogues, especially in the presence of interference, is surely greater) Huh, I never knew this. Does this mean taking ibuprofen can give you an elevated glucose reading on a blood test?

ijustlovemath 3y ago
I misspoke, it's actually acetaminophen (I'm always confusing the two!): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5950984/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5950984/ But yes, presence of acetaminophen with a naive electrochemical sensir will cause false high readings, which are VERY dangerous! The latest generation of sensors have fixed this problem, but with any new sensing tech, you need to make sure you're learning from the mistakes of the past. With a new sensing paradigm, you won't necessarily have problems with the same drugs, but knowing that this kind of constructive interference is a potential problem will help you design a more robust system.
- jfengel 3y ago
  Just a note about false readings. A diabetic with high glucose is deeply uncomfortable, and will suffer long term damage, but is not in immediate peril. The bigger danger is being low, which will lead to unconsciousness, coma, and death. Insulin brings down blood glucose. Getting insulin when not needed can be deadly. (It's a favorite of murder mystery writers.) False highs are more of a risk than false lows. Which means you may need to administer sugar to a diabetic in an emergency. But unless you're a medical professional you will never need to give them insulin.
  - ijustlovemath 3y ago
    Absolutely, the danger of a false high is that you dose insulin to correct and end up pushing yourself into a dangerous hypoglycemic state. That's why acetaminophen interference is so important to deal with! And while it's true that running a bit high (250-350mg/dL) isn't an immediate risk, DKA is still a possibility once you breach the 300s, and that will land you in the hospital.