Assessment tool helps gauge consent abilities of Alzheimer's subjects
Who should and should not give consent?
Determining the ability of patients with Alzheimer's disease to give consent for participation in research can present challenges to researchers and IRBs.
Different IRBs can vary widely as to what procedures they will accept for assessing patients, says Jason Karlawish, MD, associate professor of medicine and associate director of the Penn Memory Center at the University of Pennsylvania in Philadelphia.
"I think there's probably still a lot of variability among IRBs and investigators about what do we mean when we say we need to assess capacity and how we should do it," he says.
One well-studied instrument for this purpose is the MacArthur Competency Assessment Tool for Clinical Research (MacCAT-CR), a survey that assesses four decision-making abilities: choice, understanding, appreciation, and reasoning.
Studies of the instrument itself had shown it to be a reliable tool when used with patients who had mild-to-moderate Alzheimer's disease. Now, Karlawish and his colleagues have studied it being used in an actual clinical trial. They found that results from one of the subscales — the one measuring understanding — tracked well with experts' opinions as to whether a patient was capable of providing consent. Results were published in a recent issue of the American Journal of Geriatric Psychiatry.1
"In our paper, we're not even pushing the value of the other scales [included in the MacCAT-CR], we're saying if you just use the understanding subscale of the MacCAT, you get some decent information to structure your assessment of whether someone has adequate decisional capacity," he says.
Subjects, partners tested
Karlawish's group studied 59 subjects who were participating in a clinical trial of simvastatin, a cholesterol-lowering drug being studied in the treatment of mild-to-moderate Alzheimer's disease. Each subject was accompanied by a study partner, an adult relative or friend whom the subject trusted and who could serve as a knowledgeable aide to the subject.
"From the pragmatics of designing and conducting successful clinical trials with patients with Alzheimer's disease, you need a second person who's going to make sure that the person comes in for their visits, takes their medication, and also helps assess how the person is doing," Karlawish says.
The MacCAT-CR was administered to both the subjects and the study partners, with the study partners serving as a control group. The instrument itself is a semi-structured interview that is adapted to fit the specific information from the trial.
"This is not an instrument that has pre-specified question with answers," Karlawish says. "It lets you plug relevant information from your clinical trial into structured questions with standardized scoring criteria."
The patient and study partner would have a written summary of the clinical trial, organized according to the sections outlined in the informed consent. After each section was read aloud, the interviewer would ask if there were any questions, answer them, and then administer the questions from the MacCAT-CR pertaining to that section. Those results were tabulated.
Afterward, an audiotape of the interview was given to three consulting psychiatrists who, without seeing the score or knowing the severity of the subject's illness, judged for themselves whether they thought the subject had sufficient capacity to give consent on his or her own.
Using a consensus of at least two of three judges, 39 patients (53%) were found capable of giving their own consent. Comparing those results to the scores from the MacCAT-CR, the investigators found the scores — particularly the understanding subscore — highly predictive of the expert's opinion.
"I think that it is perfectly reasonable to say that we now have a method that allows an investigator to perform a semi-structured assessment of decisional ability so that they can make a reasonable judgment of whether someone's capable of giving their own informed consent," he says.
No set cut-point
Karlawish doesn't believe that it's necessary, or even desirable, to have one set cut-point for the MacCAT-CR — a score below which a subject is always considered incapable of giving consent. He says that cut-point could fluctuate from study to study, depending upon the risks involved. He notes previous studies have shown that experts' judgments of competency are dependent upon the risks of the research.
He says the next step is for investigators to outline the process they have in place for assessing this decisional capacity.
"They need to set aside concerns about whether we're talking about competency or capacity," he says. "What we're simply talking about here is whether this particular subject is capable of making the decision of being in this particular study."
Reference
- Karlawish J, Kim SY, Knopman D, et al. Interpreting the clinical significance of capacity scores for informed consent in Alzheimer disease clinical trials. Am J Geriatr Psychiatry 2008;16:568-574.
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