The MacArthur Competence Assessment Tool for Clinical Research (MacCAT-CR) provides a semi-structured assessment format for evaluating abilities related to the decisional capacity of subjects in clinical research. Four component abilities of a decisional capacity standard are assessed: understanding, appreciation, reasoning, and choice. Administration of the instrument begins with the disclosure of selected information about a given research project, on the basis of which these abilities are measured. The MacCAT-CR, which takes 15 to 20 minutes to administer, has demonstrated good reliability and validity and has been used both to explore the relative abilities of different subject groups and to assess the capacities of particular research subjects prior to entry into studies.
Informed consent of research subjects is a nearly universal requirement of ethical codes, federal regulations, and common law. For subjects’ consent to be valid, they must be competent (i.e., they must have adequate decisional capacity—the terms are used interchangeably in this entry) to offer consent. Because persons are generally presumed to be competent to make decisions of all sorts, barring evidence to the contrary, the question of whether subjects are competent does not arise for most research subjects; the casual interactions between subjects and researchers are sufficient to sustain the presumption of subjects’ capacity. However, some subject groups may have an elevated probability of incapacity, making it desirable, particularly in higher-risk studies, to perform an explicit assessment of their capacity. The demonstrated variability in clinical judgments of competence has encouraged the development of competence assessment instruments for this purpose.
The MacCAT-CR grows out of the four-part conceptualization of decisional capacity that underlay the MacArthur Competence Assessment Study and that is based on existing case law; statutes; and bioethical, psychological, and medical literature. Understanding is the first of these four components of competence. Research subjects, at a minimum, must have the ability to understand the basic elements of disclosure required by the U.S. Federal Common Rule, including the purpose of the research project, the procedures involved, material risks, possible benefits, and alternatives to research participation. The second component, Appreciation, reflects the importance of subjects’ abilities to apply the disclosed information to their own situations, including their recognition that the research project is aimed at generalizable knowledge, not at optimizing the treatment they receive, and that they are truly free to decline to participate without penalty. Reasoning, the third component, focuses on subjects’ abilities to manipulate the information disclosed to them, comparing and weighing the consequences of the alternatives before them. The final component is Choice, the ability to select the desired option and to sustain a consistent decision.
Because the information that subjects must understand will differ across research projects, the MacCAT-CR provides a format for disclosure of study-specific information that is standardized for all subjects in a given research study. Following disclosure of discrete informational elements, subjects’ understanding is queried by asking them to paraphrase the disclosure about specific items. Appreciation questions can be modified, if necessary, according to the nature of a given project but reasoning and choice questions are fixed. There is no effort to provide the kind of comprehensive disclosure typically embodied in informed consent forms or to measure understanding and appreciation of, or reasoning about, all aspects of the study. Rather, the MacCAT-CR offers a virtual “biopsy” of subjects’ abilities related to competence, on the assumption that the sampled data will be typical of their abilities in dealing with a complete disclosure.
Subjects’ responses to the MacCAT-CR items are scored in a structured fashion, with scores aggregated on scales for each of the four abilities being assessed. However, composite scores across all four scales are not generated, because poor performance on any one of the relevant abilities may indicate significantly impaired capacity, rendering a composite score meaningless. Nor does the MacCAT-CR provide a fixed cutoff above which subjects are deemed competent to consent. The degree of capacity required for participation in a given study should reflect the characteristics of that study, including its complexity and risks. Moreover, the capacity demanded of subjects at risk for decisional impairment (e.g., persons with mental illnesses, developmental disabilities, dementia, and serious medical disorders) ought not to exceed the abilities demonstrated by the general population. Finally, decisions about capacity should take into account clinical data that may not be reflected in assessment scores. Although investigators or institutional review boards can set MacCAT-CR cutoffs for particular studies, the instrument is designed to be used as an aid to clinical judgment, with investigators retaining the discretion to determine whether subjects are capable of consenting.
Use of the MacCAT-CR for research on decisional capacity and to screen subjects for entry to research projects has demonstrated that the instrument can be scored reliably, and that it shows good construct and convergent validity. Studies have been performed to date with samples of persons with depression, schizophrenia and related psychotic disorders, Alzheimer’s disease, mental retardation, and HIV infection and with prisoners, forensic patients, and parents of neonatal research subjects. Impairments in the abilities measured by the MacCAT-CR correlate strongly with cognitive impairments on neuropsychological tests and correlate more variably with psychotic symptoms. Thus, increasing levels of decisional abilities are found as one moves from subjects with Alzheimer’s disease to those with schizophrenia, depression, and general medical illnesses. Further research is required to determine the impairments associated with varying levels of depression and with medical conditions in which the disorder itself or its treatment may affect mentation.
Screening of potential research subjects with the MacCAT-CR has demonstrated that subjects, especially those with mental illnesses, who score poorly on initial administration can often experience improved decisional capacities with remedial educational efforts. As might be expected, levels of understanding show the greatest response to additional education, with lesser impact seen on appreciation and reasoning. Nonetheless, these studies have suggested that many research subjects can learn the information required to give a competent consent if afforded extra assistance for doing so. Thus, screening for decisional capacity accompanied by remedial education may result in better informed subjects capable of giving consent on their own rather than in the exclusion of large numbers of subjects or in a resort to substituted consent.
- Appelbaum, P. S., & Grisso, T. (2001). MacArthur Competence Assessment Tool for Clinical Research (MacCAT-CR). Sarasota, FL: Professional Resource Press.
- Grisso, T., & Appelbaum, P. S. (1998). Assessing competence to consent to treatment: A guide for physicians and other health professionals. New York: Oxford University Press.
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