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


METHODS
Cross-sectional interview.


METHODS
Thirteen sites participating in a randomized and placebo controlled study of simvastatin for the treatment of mild to moderate AD.


METHODS
Persons with mild to moderate AD and their study partners enrolled in the simvastatin clinical trial.


METHODS
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 (kappa = 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.


CONCLUSIONS
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.
Department of Medicine, Alzheimer's Disease Center, Leonard Davis Institute for Health Economics, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, School of Medicine, PA, USA. Jason.karlawish@uphs.upenn.edu
Jason
J
Karlawish
Scott Y H
SY
Kim
David
D
Knopman
Christopher H
CH
van Dyck
Bryan D
BD
James
Daniel
D
Marson
D000544:Alzheimer Disease / Q000523:psychology*; D017028:Caregivers; D003430:Cross-Sectional Studies; D003657:Decision Making; D006801:Humans; D007258:Informed Consent; D007406:Interview, Psychological; D016743:Mental Competency; D015588:Observer Variation; D012372:ROC Curve; D016032:Randomized Controlled Trials as Topic; D035842:Research Subjects / Q000523:psychology*; D012680:Sensitivity and Specificity; D016037:Single-Blind Method