4 ms·

I don't know too much detail about theranos, but is that really the case? The article says they needed to go to 6-9 drops, is that a dealbreaker for what they w

by IanCal 11y ago

I don't know too much detail about theranos, but is that really the case? The article says they needed to go to 6-9 drops, is that a dealbreaker for what they wanted to do?

adevine 11y ago
Getting 6-9 drops of blood from a finger tip is not easy - you have to ask "Is it really a benefit over a venous draw if it's much more difficult?" At some point I think it makes it easier to instead just focus on super-fine needles, and the need to draw less blood, from venous draws.
- baldfat 11y ago
  I seriously don't feel any pain 50% of the time I give blood and when I do it is a very mild prick. Usually its just the rubbing alcohol didn't all evaporate.
- mikecsh 11y ago
  "Super-fine" cause mechanical haemolysis and will give inaccurate results for many routine blood tests
  - jacobolus 11y ago
    For anyone who isn’t a doctor / biologist: “Mechanical hemolysis” means the needle is bursting red blood cells, leaking their cytoplasm into the blood plasma.
- IanCal 11y ago
  Yes, that's true. I had thought about simply squeezing the finger to get some more but that appears to be a problem for the results too: > Morris et al7 believe the higher variability of capillary blood compared with venous blood is due to the presence of extracellular fluid in capillary samples. In clinical practice, milking of the finger by insufficiently trained health care workers may result in even greater drop-to-drop variability than shown here. http://ajcp.oxfordjournals.org/content/144/6/885.full http://ajcp.oxfordjournals.org/content/144/6/885.full It's a very interesting problem. They didn't even see all the donors end up with the same average from drops as from a venous draw.
drcode 11y ago
Also, I see nothing in the study that precludes the possibility that some of the variability cannot be mitigated with statistical methods. (For some reason the last time I posted a comment like this I was heavily downvoted by people claiming that the type of error in this case is somehow not amenable to a statistical solution, but as far as I could tell no convincing argument or evidence was given for such an assertion.)
- IanCal 11y ago
  I think they can't make a strong claim about it but some of the donors didn't seem to have the same results from an average of the drops and the other blood draw > Our data also suggest that collecting and analyzing more fingerprick blood does not necessarily bring the measured value closer to those of the donor’s venous blood (Figures 1D and 2D). For example, donor B’s hemoglobin and WBC concentration were similar for venous blood and fingerprick in drop 1 but became less concordant with additional drops, while donor C’s fingerprick measures came closer to the venous measures with additional drops. These data may represent true differences between fingerprick and venous blood, or they may be the result of errors in collection (such as leaving the tourniquet on for too long during a venous draw). Further research is needed to determine how common these patterns are. Also: > Morris et al7 believe the higher variability of capillary blood compared with venous blood is due to the presence of extracellular fluid in capillary samples. In clinical practice, milking of the finger by insufficiently trained health care workers may result in even greater drop-to-drop variability than shown here. This may present more of a risk for at-home testing if you need to make sure that the person hasn't squeezed their finger at all. Quite an interesting set of problems that I'd not really considered before. Full article: http://ajcp.oxfordjournals.org/content/144/6/885.full http://ajcp.oxfordjournals.org/content/144/6/885.full

by IanCal 11y ago

I don't know too much detail about theranos, but is that really the case? The article says they needed to go to 6-9 drops, is that a dealbreaker for what they wanted to do?

adevine 11y ago

Getting 6-9 drops of blood from a finger tip is not easy - you have to ask "Is it really a benefit over a venous draw if it's much more difficult?" At some point I think it makes it easier to instead just focus on super-fine needles, and the need to draw less blood, from venous draws.

baldfat 11y ago
I seriously don't feel any pain 50% of the time I give blood and when I do it is a very mild prick. Usually its just the rubbing alcohol didn't all evaporate.
mikecsh 11y ago
"Super-fine" cause mechanical haemolysis and will give inaccurate results for many routine blood tests
- jacobolus 11y ago
  For anyone who isn’t a doctor / biologist: “Mechanical hemolysis” means the needle is bursting red blood cells, leaking their cytoplasm into the blood plasma.
IanCal 11y ago
Yes, that's true. I had thought about simply squeezing the finger to get some more but that appears to be a problem for the results too: > Morris et al7 believe the higher variability of capillary blood compared with venous blood is due to the presence of extracellular fluid in capillary samples. In clinical practice, milking of the finger by insufficiently trained health care workers may result in even greater drop-to-drop variability than shown here. http://ajcp.oxfordjournals.org/content/144/6/885.full http://ajcp.oxfordjournals.org/content/144/6/885.full It's a very interesting problem. They didn't even see all the donors end up with the same average from drops as from a venous draw.

drcode 11y ago

Also, I see nothing in the study that precludes the possibility that some of the variability cannot be mitigated with statistical methods. (For some reason the last time I posted a comment like this I was heavily downvoted by people claiming that the type of error in this case is somehow not amenable to a statistical solution, but as far as I could tell no convincing argument or evidence was given for such an assertion.)

IanCal 11y ago
I think they can't make a strong claim about it but some of the donors didn't seem to have the same results from an average of the drops and the other blood draw > Our data also suggest that collecting and analyzing more fingerprick blood does not necessarily bring the measured value closer to those of the donor’s venous blood (Figures 1D and 2D). For example, donor B’s hemoglobin and WBC concentration were similar for venous blood and fingerprick in drop 1 but became less concordant with additional drops, while donor C’s fingerprick measures came closer to the venous measures with additional drops. These data may represent true differences between fingerprick and venous blood, or they may be the result of errors in collection (such as leaving the tourniquet on for too long during a venous draw). Further research is needed to determine how common these patterns are. Also: > Morris et al7 believe the higher variability of capillary blood compared with venous blood is due to the presence of extracellular fluid in capillary samples. In clinical practice, milking of the finger by insufficiently trained health care workers may result in even greater drop-to-drop variability than shown here. This may present more of a risk for at-home testing if you need to make sure that the person hasn't squeezed their finger at all. Quite an interesting set of problems that I'd not really considered before. Full article: http://ajcp.oxfordjournals.org/content/144/6/885.full http://ajcp.oxfordjournals.org/content/144/6/885.full