Getting blood from someone's finger will lead to incorrect results in many tests because other things diffuse into the blood. The things can lead to very inaccurate results. This is a BIG problem for Theranos.
It is conceivable that they could use software to correct for this. Is there is something they can measure that indicates the amount of dilution with interstitial fluid,there might be a way to take account of it. Similarly you'd want to correct for hemolysis
I doubt that they'd be able to correct this with software. Take for example Mineral X. A concentration higher than 1mg/ml of X in blood may indicate disease D. Imagine that the tip of the finger has a much higher percentage of X than any other body parts. In testing for D you'd get a reading that may or may not be wrong as you wouldn't know if a high concentration of X is as a result of disease D or as a result of the machine's inherent error. Your screwed both ways. Theranos should understand that it isn't just a traditional software company that can release an MVP for the public. One screw up and their reputation is tarnished for ever. Just ask Volkswagen ;)
