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Showing competence in the cognitively impaired
- Trevor Thompson (27 February 1999)
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Competence to complete advance directives
- Adrian Treloar (5 March 1999)
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The test may have face validity only!
- S Teunisse (23 March 1999)
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Authors' reply: Competence to complete advance directives
- Seena Fazel (9 April 1999)
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Trevor Thompson, Higher Professional Training Fellow Department of General Practice, University of Glasgow
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The authors are surely right in asserting that understanding future clinical situations should be a prime determinant of the validity of a person's advance directive. There will be those with formal cognitive impairment who can do just that - given a sufficiently patient interlocutor. The authors show that their assessment of capacity based on clinical vignettes has the same discriminatory power as the conventional scale of Silberfeld. What they do not demonstrate is that this new vignette-based tool can judge competent those who are also mildly demented. If this is not the case then the new tool is as good but not demonstrably better than what we have already for judging competence. As an aside it would be interesting to know what choices the subjects in the two groups did in fact make. The second vignette exemplifies one of the more difficult scenarios with respect to living wills. The typical living will, eg that suggested by Robertson (1), eschews invasive treatment to sustain life where the will-maker has been judged by two doctors to be suffering from irreversible cognitive impairment preventing participation in decision making. This loss of competence is a sort of proxy for quality of life - ie "if I can't make decisions for myself that indicates that the quality of my life is so poor that it is not worth sustaining". But the patient in this vignette has, let us assume, lost formal capacity, but maintains what we could possibly conclude to be a reasonable quality of life - "happy and contented", and still able to recognize relatives. Had he or she made a prohibitive living will it might be difficult for doctors and relatives not to wish to proceed - at least to investigations. The ethical justification for this would be that the patient could not have fully appreciated that they could be both mildly demented and happy and contented when they made the directive. In cases of more severe dementia I think the whole thing becomes a lot simpler. The advantage of this boarderline scenario is that it throws up many issues upon which the person can demonstrate competence. However if it is to be used as one of two possible vignettes in a discussion of living wills with an interested person, say in a primary care context, then it may be too ambiguous. |
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Adrian Treloar
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Sir The paper by Fazel et al1 describes a way in which the competence of patients to make contemporaenoeous decisions can be assessed. However competence to complete advance directives is a very different issue. The authors rightly point out that competent people may not be well placed to make decisions regarding their future incompetent selves, but fail to acknowledge that this is equally the case in people with early dementia. Vague statements like “I do not want to be a burden to others” are not, in my view adequate evidence of capacity. Having signed such a statement, an incompetent patient may be refused treatments which offer sympotomatic benefit or improved quality of life. As the British Geriatric Society pointed out “most patients assume that an AD applies solely to non- intervention in terminal illness. They do not appreciate that it would lead to non-treatment of a curable disease. In consequence, misapplied ADs could cause patients to suffer a lengthy, painful, degrading bed-ridden existence - precisely what they sought to avoid. Whereas without the AD, they could have been rehabilitated to a satisfactory lifestyle.”2 Given the problems with Advance Directives, it is greatly to be hoped that legislation will not make Advance Directives legally binding. The House of Lords Select Committee thought that even those without dementia should not be able to sign directives which are legally binding. The propect of people with demeintia being prompted to sign documents that could legally ban doctors from appropriate treatments which offer a good prospect of symptomatic improvement is unwelcome indeed. Yours sincerely Adrian Treloar Consultant and Senior Lecturer in Old Age Psychiatry 1 Fazel S, Hope T and Jacoby R. Assessment of competence to complete advance directives: validation of a patient centred approach. BMJ 1999;318: 493-7. 2 Millard P. British Geriatrics Society statement (1995). Legally binding wills or advance directives. BGS London. |
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S Teunisse
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We read with interest the article by Fazel et al., that described an instrument for the assessment of competency to complete advance directives, which appears to be reliable, valid and ready for use in clinical practice. 1 However, we believe certain aspects require clarification before the clinical usefulness of the test is assured. First of all, who is this test meant for? Different groups are suggested in different parts of the text. Is it meant to differentiate between competency and incompetency in demented patients, in the broader group of cognitively impaired patients, or in elderly volunteers? If the test aims to assess competency in dementia, test-retest analysis should include data of demented patients only, because fluctuations in functioning in this group are more common. The reported test-retest correlation was mainly based on data of non-demented subjects and there is a likelihood of overestimation of the reliability of the test for demented subjects. Furthermore, the test discriminated between non-demented volunteers and demented subjects, but the influence of education on the results was not considered. Taking into account that volunteers are often well educated, the results may reflect differences in educational background instead of differences in competence. Finally, and probably most importantly, the "gold standard" and test result were not independently obtained in the present study and therefore the test could be considered as having "face" validity only. Using this gold standard for the calculation of a cut-off score and the fact that it was based on only 19 (including 8 non-demented) subjects, necessitates further development considering the huge consequences the application of this test may have in clinical practice. This may also apply to shortening the test by using two instead of three vignettes without checking its effect on the reliability of the test result. In conclusion, there is a critical need for standardised instruments to guide competence measurement in many domains, including consent to treatment, engaging in research and making choices about living arrangements. The described study by Fazel et al. is a welcomed initial step. 1. Fazel S, Hope T, Jacoby R. Assessment of competence to complete advance directives: validation of a patient centred approach. BMJ 1999;318:493-7 (20 February). Saskia Teunise, Senior Psychologist (1) Psychology Department Community Mental Health Unit Sarah Eagger, Senior Lecturer in Old Age Psychiatry (1+2) James Warner, Senior Lecturer in Old Age Psychiatry (1+2) (1) St Charles Hospital, Exmoor Street, London W10 6DZ (2) Imperial College School of Medicine |
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Seena Fazel, Wellcome Research Registrar Section of Old Age Psychiatry, University of Oxford, Warneford Hospital
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We are grateful to the authors of these letters and welcome the discussion. Thompson indicates the similarity in results using the Silberfeld method and this instrument. In the paper, we argue that an assessment tool needs to be theoretically sound and psychometrically robust. The Silberfeld method is neither. To our knowledge, it has never been tested for reliability and validity. Although the Silberfeld method turns out to be positively correlated with the instrument we propose, it is also the case that the MMSE is highly correlated with our assessment method. This is not surprising as any method of assessing cognitive function is likely to correlate well with any measure of competence - since lack of competence is caused principally by impaired cognitive function (particularly in dementia). However, assessment of competence should not be replaced by an assessment of cognitive function for two reasons: first, the correlation is not perfect, and a number of individuals would therefore be misclassified; second, it would be legally invalid. Thompson asks further questions about whether our tool can judge mildly demented persons to be competent and what treatment choices subjects made in the vignettes. These are both good questions and will be the subject of forthcoming papers. Our vignette-based tool does indeed judge a proportion of those who are mildly demented to be competent. Thompson also raises the question of whether the second vignette is too ambiguous to be used in an advance directive. We do not propose that these vignettes should be the basis of advance directives. They are useful, as he admits, because they throw up many issues upon which the person can demonstrate competence to complete advance directives. Treloar's comments are focused on the ethical justification of advance directives, which were not addressed in our paper. He also states that some of the criteria we use to assess competence, such as the statement "I do not want to be a burden to others", are not adequate evidence of capacity. We agree - which is why it forms only one-tenth of the scoring system in our assessment. Teunisse and colleagues ask a number of methodological questions. Their first question is on whom the test can be used. We believe it can be used on anyone, including healthy elderly people but particularly those with mild dementia (1). They also ask whether the influence of education was considered. It was tested and we administered the National Adult Reading Test (NART) to all subjects, a valid and reliable index of pre-morbid intelligence in the elderly and in mild dementia. There was no significant difference in the NART scores between the volunteers and patients with dementia. Their last point concerns the validity of the instrument. Our results go beyond face validity in that the "gold standard" was conducted by the two psychiatrists who had not conducted the initial interview, and therefore did not know what competence score the subject had received. Nevertheless we accept that further work refining this and other instruments would be worthwhile. Seena Fazel, Wellcome Research Registrar Tony Hope, Reader in medicine Robin Jacoby, Professor Section of Old Age Psychiatry, University of Oxford, Warneford Hospital, Oxford OX3 7JX Reference: 1. O'Carroll, R. The assessment of premorbid ability: a critical review. Neurocase 1995;1:83-89. |
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