Medical decision-making competence

This week’s Lancet contains a study by Raymont et al investigating the prevalence of mental incapacity in medical inpatients and associated risk factors (see also this item in Shrinkette’s blog ).

In order to judge medical decision-making competence, the authors used two tools: the MacArthur competence assessment tool for treatment (MacCAT-T), and clinical vignettes (based on something called the “Thinking Rationally About Treatment” research method).

After excluding 143 patients for severe cognitive impairment, altered level of consciousness and refusal to participate, 159 patients were interviewed. Of these, 50 (31%) were deemed lacking in capacity to make medical decisions.

Lack of capacity was correlated with increasing age and with a poor score on the Mini Mental Status Exam. The median MMSE score was 29 (out of a maximum of 30) in patients with capacity and 22 in those without capacity.

Significantly, when the clinical team caring for the patients and close relatives were asked to judge the patients’ capacity, those with capacity were correctly assessed almost 100% of the time, but those deemed lacking in capacity by the authors were judged incompetent only 25% of the time by the physicians and similarly by the relatives.

The conclusion to the abstract: “Mental incapacity is common in acutely ill medical inpatients, and clinicians tend not to recognise it. Screening methods for cognitive impairment could be useful in detecting those with doubtful capacity to consent”.
Are we really underestimating patients’ decision-making capacity as badly as this article suggests? Possibly, but I have a few reservations about the study.

The MacCAT-T tool used to assess medical decision-making capacity is a relatively new one. How valid is it? If three-quarters of physicians caring for the patients and three quarters of their relatives judged the patients who “failed” the MacCAT-T assessment to be competent, it makes me wonder as much about the validity of the tool as about the physicians’ and relatives’ assessments.

According to the authors:

MacCAT-T is a semi-structured interview that measures: (1) understanding of the disorder and its treatment, including associated benefits and risks; (2) appreciation of the disorder and its treatment–ie, how the patient understands they could be specifically affected, which usually entails some level of insight; (3) reasoning, which assesses the processes behind the decision and ability to compare alternatives in view of their consequences; and (4) the ability to express a choice.

I am no expert in such assessment tools, but it seems to me that this sort of assessment might bias, for example, against people who have crackpot medical ideas. Are they necessarily incompetent?

Since the assessment of medical competence correlated well with the MMSE assessment in this study, wouldn’t we be better off relying on the MMSE itself, which is not limited to medical decision making capacity? The determination of a patient’s specific competence to make medical decisions seems somehow more paternalistic and prone to bias than a more general assessment of mental status.

2 thoughts on “Medical decision-making competence

  1. Matthew Hotopf

    [Author’s comments]

    I’m flattered to see our paper highlighted here. The key point about capacity is that it is situation specific (ie “functional”). This is why the MacCAT-T is an appropriate interview to assess it and the Mini-Mental State Examination is not. The fear that the MacCAT-T will bias the study against people with “Crackpot” medical ideas, is misplaced. The interview allows a patient to make what many people would consider to be a foolish choice and still be rated as having mental capacity. It tests the process by which a choice is made and expressed, rather than the choice itself.

    The problem with simply using a measure like the MMSE is that it would rely on a “status” approach, whereby all individuals who scored below a given threshold would be deemed incapacitated, without taking into account the nature of the decision. This is a far more paternalistic approach than the “functional” one used in the MacCAT-T. Individuals with cognitive impairment are often perfectly capable of making relatively simple decisions, but may not be capable of making more complex ones (which, typically, includes many medical decisions which are heavy with appraisal of risks and benefits).

    Furthermore, mental capacity is more than just a cognitive phenomenon – in other words, there may be many factors which affect “appreciation” which are not to do with the mechanics of memory and comprehension. The simplest example is the effect psychosis has on mental capacity – an individual may have a delusional belief that doctors are attempting to poison him, and therefore refuse treatment for a psychotic disorder. The same individual may well have excellent cognitive functioning. Appreciation may also be affected by affective disorders (depression and mania) and even powerful emotions in an individual with an adjustment disorder.

  2. Beth Leopold

    I’m a public health professional who discovered this discussion by accident while looking for something else, but I just have to comment. I’ve had regular medical decision-making experience as a patient with a fairly obscure neurological pain syndrome and while supporting both parents through their final illnesses. I’m facinated by this detached discussion of competency of patients to make medical decisions. In my experience most high-stakes medical choices are offered to patients verbally, without well prepared written, objective information, in an atmosphere highly charged with emotion, by medical professionals who have not been evaluated on their communication skills.

    My observation is that doctors, who have the advantage of years of study and preparation, are quite willing to make the easy decisions. The more risky the choices, the more the decision shifts to patient and family. The most common example is choice of medication in this environment of heavy medication marketing. Doctors seldom discuss the full range of meds and offer me choices. The way I get a choice is after I develop a reaction to the popular med, then I’m offered the old stand-by. But my favorite example is when I had to fight to keep my dad from being moved from a step-down unit to a med-surg floor after he showed a modest post-surgical improvement. My argument was that, in my judgement, the improvement wasn’t well enough established for the careful supervision and observation which is characteristic of the step-down unit to be discontinued. I was told as a family member, I wasn’t qualified to make that decision. Funny how I became qualified to make end of life decisions about my dad within the week.

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