Assessment of capacity for medical decision making.

Determination of a patient's capacity for medical decision making can be simple or complex, depending on the issue being considered; likewise, the degree of capacity required to make decisions varies with the complexity of the situation. A capacity examination is a focused and impartial evaluation of mental status and medical, surgical, psychiatric, and psychosocial histories. The examination is composed of several basic steps, beginning with an assessment of the patient's ability to communicate, followed by determination of his or her understanding of the proposed care, followed by the patient's rationale for decisions about that care. When a patient is deemed to lack capacity, mechanisms should be in place to ensure the patient receives the care needed. This article provides an overview of the concept of capacity, how it is determined, and how to proceed when the patient is found to lack it.