[Limits to the power of medicine to define disease and risk factor, and quarternary prevention].

Patient safety means to avoid unnecessary harm produces by health care activities. Quaternary prevention is a medical activity that try to avoid or decrease the health consequences of unnecessary or excesive health care. Physicians' definition of health, risk factor and disease justify many unnecessary medical interventions. It is critical to control an excesive medical technological actitude that allows excesive medical interventions. The medical power of definition of health and disease transform risk factor in a border which usually overlap with the disease field. We need research on quaternary prevention, and to develop activities of quaternary prevention which help in stopping the dissemination of health care (preventive, curative, diagnostic or therapeutic) of little value.