Alzheimer's Disease Education and Referral Center

Interviews can help judge AD patients' capacity for informed consent

March 17, 2009

Cognitive impairment in people with mild to moderate Alzheimer’s disease (AD) can diminish their capacity to provide informed consent for clinical trials, presenting ethical challenges for researchers. A semistructured interview can help determine which people are capable of giving their own informed consent, according to an NIA-supported study in the American Journal of Geriatric Psychiatry.

The MacArthur Competency Assessment Tool for Clinical Research (MacCAT-CR), an interview tool that assesses 4 decision-making abilities—choice, understanding, appreciation, and reasoning—was administered to 59 people with mild to moderate AD, who were participating in a 13-site clinical trial. Researchers, led by Dr. Jason Karlawish of the University of Pennsylvania School of Medicine in Philadelphia, adapted the interview procedure by allowing individuals to keep a summary of the trial as they answered questions. Three psychiatrists independently reviewed the MacCAT-CR interviews and decided the strength of each subject’s capacity to give informed consent.

The researchers found that MacCAT-CR scores, specifically the subscores for understanding, had the best ability to discriminate which subjects were able to provide informed consent. Nearly half of the study group (47 percent) was judged not capable of providing their own consent. However, the authors note, this proportion could vary depending on the risk of the study and the techniques interviewers use to administer the MacCAT-CR. They caution other investigators against using this tool alone to decide which people with AD are capable of providing informed consent, but to use its results “as evidence to guide what is ultimately an ethical judgment.”


Karlawish, J., et al. Interpreting the clinical significance of capacity scores for informed consent in Alzheimer disease clinical trials. Am J Geriatr Psychiatry. 2008. 16(7):568-74. Epub 2008 June 12.

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