Theranos gets the press because of its attractive founder and large valuations... but far more eminent scientists have been working on the same microfluidics technology for years. The real problem is that blood in small quantities is a pudding rather than a liquid, and not identical in composition to larger samples of blood.

Not to be dumb, but I also wonder... is VOLUME of blood draws really that big a barrier to cheap diagnostics? I have no issues with having my blood drawn personally -- I was once a test subject in a medical study that took like 30 vials of blood! I was pale as a veal -- so the needle factor doesn't matter to me. I guess the phlebotomist labor might be more of an issue... but even a common finger-prick test like hemoglobin isn't self-serve.

Volume is definitely an issue for some people. Not everyone wants to give girls of blood.