Hi, pathology resident here. Even with large volume venous blood draws, you can change the values quite substantially. one of my professors likes to tell the story how just by pumping his fist as is usually directed by The phlebotomist, he was able to change his potassium level from 4 to 5 to 6 to 6.5. This is the difference between normal and starting to worry about heart problems. so it is far from shocking at least to the experienced, that this is a problem for microfluidics.
This essentially equivalent to a sampling error problem. A large venous sample (10 mL) is enough to get a pretty good average. Microliters of blood from any given location in the body are likely to be different from microliters somewhere else in the body. I seriously doubt anyone in a clinical lab would be surprised by these results.
This study is at the "microtiter" scale, which is the scale that companies such as theranos are trying to take advantage of.
Microfluidics is largely an industrial field rather than academic.
>Not only does it seem like a very fundamental question to have already asked...it doesn't even seem like a very difficult study to do.
Yeah, well, that's the difference between Silicon Valley and academia.
SV doesn't want to hear about results that invalidate their business model.