Each year in the US, a quarter of a million deaths are attributable to medical error. If the number shocks, on some level you already knew it was so. Everyone knows someone - perhaps it was yourself - who has suffered miserable treatment in American hospitals, part of the most elaborate, most extensive and expensive health-care system in the world. But it is perhaps the most inefficient. Misdiagnoses, wrong prescriptions, operating on the wrong patient, even operating on the wrong limb (and amputating it).