Theranos isn't even at the leading edge of blood testing. There are now hand-held FDA-approved immediate blood testing devices.[1][2][3] Most of these require smaller amounts of blood than a remote lab, although more than a drop. Theranos is still in the send-it-to-the-lab-and-wait era. Even if Theranos' technology eventually works, it may be obsolete before it ships.
[1] https://www.abbottpointofcare.com/products-services/istat-ha... [2] http://www.epocal.com/system.html [3] http://www.pixcell-medical.com/products/in-the-pipeline