The deception is made more difficult via the significant match screening required. When I donate blood, they ask me a series of questions. I can answer as truthfully as I like. How much testing they do to the whole or processed blood likely differs widely from facility to facility.
Before donating a kidney, I went through half a dozen invasive, detailed medical exams that didn't depend on my given answers at all.
Before donating a kidney, I went through half a dozen invasive, detailed medical exams that didn't depend on my given answers at all.