Interpreting the clinical significance of capacity scores for informed consent in alzheimer disease clinical trials

Jason Karlawish, Scott Y.H. Kim, David Knopman, Christopher H. Van Dyck, Bryan D. James, M. Bioethics, Daniel Marson

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


Objective: Among Alzheimer disease (AD) patients enrolled in a clinical trial, the authors assessed the ability of a standardized capacity assessment procedure to identify persons who are capable of giving their own informed consent. Design: Cross-sectional interview. Setting: Thirteen sites participating in a randomized and placebo controlled study of simvastatin for the treatment of mild to moderate AD. Participants: Persons with mild to moderate AD and their study partners enrolled in the simvastatin clinical trial. Measurements: Interviews to assess decision-making capacity using the MacArthur Competency Assessment Tool for Clinical Research (MacCAT-CR). Results: Judges blinded to the subject's clinical status had a high rate of agreement on patients capable of giving their own informed consent (κ = 0.73). The understanding subscale had the best receiver operator characteristic and an analysis of positive and negative predictive values over a range of hypothetical prevalences of incapacity to consent demonstrated the value of a range of understanding cut-points. Conclusion: Among mild to moderate AD patients, enrolled in an actual clinical trial, these results suggest evidence based guidelines for using the MacCAT-CR understanding subscale to help guide judgments about whether a patient has the capacity to consent.

Original languageEnglish (US)
Pages (from-to)568-574
Number of pages7
JournalAmerican Journal of Geriatric Psychiatry
Issue number7
StatePublished - Jul 2008


  • Alzheimer disease
  • Decision making capacity
  • Informed consent

ASJC Scopus subject areas

  • Geriatrics and Gerontology
  • Psychiatry and Mental health


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