[Medical risk assessment--using the example of cancer screening].

Knowledge about the benefits and harms of cancer screening is essential for physicians and patients making informed decisions. However, we will demonstrate that many physicians' and patients' knowledge of cancer screening is alarmingly limited. Only about 5 percent of the patients correctly estimate its benefits, while most either highly overestimate these benefits or do not know about their magnitude. Relying on a doctor's judgment alone is not always advantageous: One third of the gynaecologists investigated were ignorant of the benefits of mammography screening, and 79 percent were unable to interpret a positive result (the positive predictive value). Nor does consulting a patient brochure guarantee more knowledge, as only few brochures contain transparent and evidence-based information about the benefits and harms of cancer screenings. Hence, informed consent is unlikely to take place in everyday practice. Truly informed decision making in medicine requires more evidence and transparency for patients as well as a better statistical training of physicians.