Identifying ambulatory cancer patients at risk of impaired capacity to consent to research.

Ethicists and others have expressed concerns that some patients with cancer might lack adequate decision-making capacity to give consent for research. Although this concern is plausible, it is not known what patient characteristics might be used to identify those patients who are at risk and who therefore should undergo a formal assessment of decision-making capacity. Forty-five patients with cancer were presented with a description of a randomized controlled trial, accompanied by an Institutional Review Board-approved consent form. Two raters who were blind to all patient characteristics assessed decision-making capacity using the MacArthur Competency Assessment Tool for Clinical Research. These scores were summarized in overall capacity judgments using criteria established by a panel of experts. Subjects also completed a symptom rating scale and a battery of neuropsychiatric tests. No relationship was observed between symptom severity and any domain of decision-making capacity (understanding, appreciation, reasoning, ability to express a choice) or summary judgments. However, several other patient characteristics, including age, education, and selected neuropsychiatric test results, were found to be strongly associated with capacity scores. These data suggest that several patient characteristics, such as age, education, and tests of cognitive functions, may help investigators to identify patients with impaired capacity to give consent for research.