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Voluntary informed consent is, with rare exceptions, a necessary, albeit not sufficient, defining precondition of ethical clinical treatment, and it is essential for enrollment in clinical research trials.
Voluntary informed consent is, with rare exceptions, a necessary, albeit not sufficient, defining precondition of ethical clinical treatment, and it is essential for enrollment in clinical research trials. The validity of an individual's consent is contingent not only on it being given in a voluntary context and with full disclosure of all relevant information (in language intelligible to the recipient) but also on the consenting person having sufficient mental capacity to make a meaningful decision.1,2
Explicit and systematic evaluation of decisional capacity is often thought of in the context of legal competency proceedings, such as when a patient with questionable decisional capacity refuses an intervention that others think necessary to his or her safety and well- being. Whether or not the treating clinician decides to conduct a systematic or explicit assessment of the patient's decisional capacity, he or she nevertheless has an ethical responsibility to ensure that the patient who agrees to a recommended intervention actually has sufficient capacity to understand what will be involved in the treatment.1,2
There are few guidelines that specify when explicit assessment and documentation of an individual's consent capacity is needed. However, such assessment and documentation may be particularly prudent when the individual consents to complex or high-risk interventions, when there are multiple viable treatment options with different or complex risk-benefit profiles, and/or when the patient has marked cognitive deficits or other risk factors for impaired decisional capacity.3,4
As detailed in the model put forth in 2 studies by Appelbaum and colleagues,5,6 decision-making capacity is generally defined by 4 functional tasks:
These abilities are all framed in reference to a specific decision. The ethically relevant question is not the patient's general (typical) capacity for making decisions, but rather his capacity to make the particular decision at hand.
This 4-component model of decisional capacity was developed, in part, from consideration of the abilities deemed through case law as relevant to establishing competency.5,7,8 However, decisional capacity and competence are not synonymous, the former is a clinical construct and the latter is a legal term. Although courts generally give weight to the evidence an examining clinician provides regarding a patient's decisional capacity, the ultimate determination of competence is made by the court, not by a physician or other clinician.9 In contrast, the treating clinician retains ethical responsibility for ensuring that the patient has the capacity to consent to the treatment(s).
Instruments for assessing decisional capacity
Unaided by structured methods, there tends to be low interrater reliability among clinician judgments of decisional capacity.10,11 Fortunately, interrater reliability can be improved with specific guidance on the standards for decisional capacity,12 and a number of structured or semistructured instruments have been developed to assist clinicians to systematically evaluate their patients' decisional capacity relative to such standards.13-15
In a recent comprehensive review we identified 15 published questionnaires or instruments that assess capacity to consent to treatment (as well as 10 instruments for assessing capacity to consent to research).13 Nine of the 15 treatment consent capacity measures provide for assessment of all 4 dimensions of decisional capacity, and evidence of at least adequate interrater reliability (= 0.80) was available for 7 of these 9 measures (Table).13
One primary methodological distinction among capacity assessment instruments is whether patients' decisional capacity is evaluated in reference to an actual treatment option or in reference to hypothetical vignettes. Of the 7 measures, 4 use hypothetical vignettes, whereas the other 3 evaluate a patient's response to actual diagnosis and proposed treatment(s).
The instruments that use hypothetical vignettes have the advantage of standardized methods and facilitate comparison of responses and scores across patients and settings, thus they tend to be ideal for empirical studies of decisional capacity. However, in a clinical context, their predictive validity and generalizability is less clear. On the other hand, tailoring content to the individual's actual choice clearly increases the ecological validity of the assessment but complicates comparison of results from different treatment scenarios. Because the specific information to be understood, appreciated, or reasoned about is variable, the degree to which supporting data on the reliability and validity of the instrument tailored for one treatment scenario generalizes to other decisions is often unclear.
In addition, clinicians who use these instruments should keep in mind the specific item content. Although there appears to be good inter-instrument consistency in the understanding component of decisional capacity, subjective as well as empirical comparison of the subscales from various instruments suggests some discrepancies in the appreciation and reasoning components.23-25
A persistent methodological challenge in establishing the criterion or predictive validity of decisional capacity instruments is the lack of a gold standard against which the current measures can be evaluated. In lieu of an ideal criterion, validity data for these instruments have taken a range of forms, including agreement with expert or other stakeholder judgments, ability to discriminate between cognitively impaired persons and neurologically healthy individuals, and the degree of correlation or agreement with other capacity instruments and/or neuropsychological measures. (Dunn and colleagues13 provide detailed tables summarizing format content, administration time, and psychometric properties for each published instrument.)
Implementing assessment into clinical practice
Many of the best instruments for assessing capacity to consent to treatment routinely require 20 minutes or more to administer. Given the time constraints placed on many clinicians, routine use of such instruments with every patient may not be a viable option. However, the decision whether to incorporate such instruments into everyday practice need not be viewed as a dichotomous choice but rather as a graded series of options.
At the most basic level, some assessment of patient comprehension can and should be included in nearly every consent discussion with the patient. Incorporating a few basic queries into the initial information disclosure and discussion can be invaluable in identifying and quickly rectifying any initial patient miscomprehension.26,27 For instance, patients can routinely be asked to explain in their own words what they understand about the nature, purpose, risks, and alternatives to the proposed treatment. Ideally, the content of the initial and scoring criteria for such questions can themselves be standardized.26 Based on the response to such initial inqui-ries, the need for more comprehensive assessment may become apparent. Patients with marked cognitive impairments may warrant use of more comprehensive assessments before treatments are prescribed for which there is a likelihood of harm from errant decisions.
The need to explicitly assess and document capacity to consent to treatment for patients may arise even more frequently or saliently in geriatric psychiatry settings. Specifically, concern about decisional capacity may be due to a variety of factors, such as:
Moreover, because of increased physical frailty and vulnerability to medication side effects, along with increased rates of medical comorbidity and polypharmacy, patients in geriatric psychiatry clinics may face mulifaceted treatment regimens, and thus, complex risk-to-benefit profiles. Empirical data clearly demonstrate that it would be inappropriate to assume either the presence or the absence of decisional capacity solely on the basis of age, diagnosis, or similar risk factors. That is, decisional capacity is appropriately evaluated on a person-by-person (and decision-by-decision) basis. But consideration of risk factors can be helpful in deciding when routine use of more comprehensive assessments may be warranted.
Once the decision to use a capacity instrument has been reached, one is still faced with the dilemma of choosing among the various available instruments. Based on the degree of empirical support, its adaptability to a variety of situations, and the availability of a comprehensive published manual and other training materials for administration and scoring, our research group recently recommended the MacArthur Competency Assessment Tool for Treatment as the best generic choice.13 However, we also acknowledged that none of the instruments are perfect, and there are situations in which another instrument may be a better choice. (For detailed discussion and recommendations, please see the report by Dunn and colleagues.13) Few of the instruments provide definitive "cut-scores," and the ultimate determination of whether a patient has sufficient capacity to consent still depends on professional judgment.28,29
Even when an individual is found to lack sufficient capacity to make a particular decision, additional assessment may be helpful in clarifying the nature of his decision-making difficulty. Although neuropsychological tests do not provide a direct measure of capacity to make a specific choice, consideration of the overall pattern of a person's neuropsychological strengths and weaknesses can be helpful in understanding the neurophysiological source of any cognitive deficits as well as in understanding which specific information processing abilities are suboptimal.30 Such information can be exceptionally helpful in developing compensatory strategies, including enhanced consent procedures.31
1. National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research. The Belmont Report: Ethical Principles and Guidelines for the Protection of Human Subjects of Research. 1979. Available at: www.hhs.gov/ohrp/humansubjects/guidance/ belmont.htm. Accessed September 28, 2007.
2. President's Commission for the Protection of Human Subjects of Biomedical and Behavioral Research. Making Healthcare Decisions: A Report on the Ethical and Legal Implications of Informed Consent in the Patient-Practitioner Relationship. Vol 1: Report. Washington, DC; 1982.
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