[Iatrogeny: how prevalent is it, why, and how can it be reduced?].

Iatrogeny is a paradoxical domain from several points of view: it is a daily preoccupation for physicians but scientific data on its frequency and consequences are rare. The best way to reduce iatrogenic results is prevention but clearly identified preventive methods and their evaluation for efficacy are also scarce. Finally, patients dread it, but they are often the first to demand new technologies, even if evaluation is incomplete. Indeed, iatrogenic results peak when new therapeutics or diagnostic procedures first appear on the market, because a large number of patients is needed to evaluate the risk involved. A posteriori evaluation of emerging medical or diagnostic procedures, i.e., after several months of marketing, thus remains the best guarantee for improving the quality of care.