No biochem, but from what I read, it was highly doubtful that the product could even theoretically work because blood is not a completely homogeneous fluid. Concentrations of the things you want to test for vary by quite a lot if you take tiny samples from different places (esp. blood from small capillaries like in the finger tip).
That's (at least one reason) why "normal" blood draws are quite a lot of blood. By thoroughly mixing the drawn blood, you get a much better approximation of the average concentration throughout the body.
