Understanding probabilistic risk in predisposition genetic testing for Alzheimer disease.

The utility of genetic testing in preventing the onset of conditions such as Alzheimer disease (AD) depends upon categorizing individuals based on their "risk" of illness. Although no strategies to prevent the occurrence of AD have been proven effective, the promise of the new molecular medicine is based on the assumption that those "at risk" can be identified, counseled about their likelihood of developing a disease, and prescribed specific preventive interventions. We suggest that this paradigm of disease prevention through risk stratification has limitations that have not been fully explored. Within the fields of cognitive and health psychology, research has addressed how individuals understand the numeric presentation of uncertain future events; this research often focuses on the "perceptual pathology" of lay people. The uncertainty inherent in the risk estimates themselves is rarely considered, nor has research addressed how those risk estimates are created. There has been limited work to date focused on genetic risk assessment, and little is known about how individual might understand the meaning or consequences of being at genetic risk for AD. An emerging social science critique of concepts of risk in genetic medicine offers a broader perspective, examining the process of producing scientific risk estimates as well as the response of individual patients, such as the experience of embodied risk that is central to genetic testing. Making fully informed choices about genetic testing for AD may prove more difficult than our current model of ethical practice suggests.