Measuring informed consent capacity in an Alzheimer's disease clinical trial.

INTRODUCTION: Accurately and efficiently determining a participant's capacity to consent to research is critically important to protect the rights of patients with Alzheimer's disease (AD).

METHODS: Understanding of the informed consent document was assessed in 613 community-dwelling patients with mild-to-moderate AD enrolled in a randomized, placebo-controlled trial. Associations were examined between clinically determined capacity to consent and (1) patient demographics and clinical characteristics and (2) the Informed Consent Questionnaire (ICQ), an objective measurement of a participant's factual understanding and perceived understanding.

RESULTS: A total of 453 (74%) participants were determined to have capacity to consent by clinical judgment. ICQ perceived understanding, race, measures of cognitive function, and caregiver time were all significantly associated with the determination of capacity in multivariate analyses.

DISCUSSION: We found a significant association between capacity and disease severity level, caregiver time, race, and ICQ perceived understanding.