[mlashcorp]

I'm sorry but this is incorrect for a lot of blood tests. When the theranos debacle unfolded there was a paper making the rounds (no doubt leveraging on the media's attention)that argued this point for white blood cell counting. The conclusions were overblown, there is increased variability when using small amounts of capillary blood, but the tests are still useful. Furthermore, a lot of parameters are less sensitive to this heterogeneous distribution of the analyte.

Case in point. Major companies like roche and abaxis have had point-of-care medical devices that perform blood testing for various parameters that use a drop of blood.

Theranos's problem was that they said they could do pretty much every parameter under the sun, and they used an FDA loophole to operate their lab. It was later discovered that 90% of the tests were not being processed with their supposed technology.