[fullmetal]

In theory, there is no reason why our current diagnostics require the volume of blood that is drawn, or why a smaller sample wouldn't work.  Handling and analysis of smaller volumes is an engineering problem, so there is no reason why Theranos couldn't work.  The problem, of course, is that it is a tricky engineering problem, especially because blood is prone to doing all sorts of things, like clotting, that you might not want it to do (depending on the test).

What about small signals, diffusion/attenuation/sampling issues, and the large overall volume of blood in the body?  Those are the major reasons I've heard why nanoscale blood sampling isn't going to solve many biological diagnostic issues.

[fullmetal]

In theory, there is no reason why our current diagnostics require the volume of blood that is drawn, or why a smaller sample wouldn't work.  Handling and analysis of smaller volumes is an engineering problem, so there is no reason why Theranos couldn't work.  The problem, of course, is that it is a tricky engineering problem, especially because blood is prone to doing all sorts of things, like clotting, that you might not want it to do (depending on the test).

What about small signals, diffusion/attenuation/sampling issues, and the large overall volume of blood in the body?  Those are the major reasons I've heard why nanoscale blood sampling isn't going to solve many biological diagnostic issues.