Abstract
OBJECTIVE: To compare results of a specific capacity assessment administered by the treating clinician, and a Standardized Mini-Mental Status Examination (SMMSE), with the results of expert assessments of patient capacity to consent to treatment.
DESIGN: Cross-sectional study with independent comparison to expert capacity assessments.
SETTING: Inpatient medical wards at an academic secondary and tertiary referral hospital.
PARTICIPANTS: One hundred consecutive inpatients facing a decision about a major medical treatment or an invasive medical procedure. Participants either were refusing treatment, or were accepting treatment but were not clearly capable according to the treating clinician.
MEASUREMENTS AND MAIN RESULTS: The treating clinician (medical resident or student) conducted a specific capacity assessment on each participant, using a decisional aid called the Aid to Capacity Evaluation. A specific capacity assessment is a semistructured evaluation of the participant’s ability to understand relevant information and appreciate reasonably foreseeable consequences with regard to the specific treatment decision. Participants also received a SMMSE administered by a research nurse. Participants then had two independent expert assessments of capacity. If the two expert assessments disagreed, then an independent adjudication panel resolved the disagreement after reviewing videotapes of both expert assessments. Using the two expert assessments and the adjudication panel as the reference standard, we calculated areas under the receiver-operating characteristic curves and likelihood ratios. The areas under the receiver-operating characteristic curves were 0.90 for specific capacity assessment by treating clinician and 0.93 for SMMSE score (2p=.48). For the treating clinician’s specific capacity assessment, likelihood ratios for detecting incapacity were as follows: definitely incapable, 20 (95% confidence interval [CI] 3.6, 120); probably incapable, 6.1 (95% CI 2.6, 15); probably capable, 0.39 (95% CI 0.18, 0.81); and definitely capable, 0.05 (95% CI 0.01, 0.29). For the SMMSE, a score of 0 to 16 had a likelihood ratio of 15 (95% CI 5.3, 44), a score of 17 to 23 had a likelihood ratio of 0.68 (95% CI 0.35, 1.2), and a score of 24 to 30 had a likelihood ratio of 0.05 (95% CI 0.01, 0.26).
CONCLUSIONS: Specific capacity assessments by the treating clinician and SMMSE scores agree closely with results of expert assessments of capacity. Clinicians can use these practical, flexible, and evaluated measures as the initial step in the assessment of patient capacity to consent to treatment.
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References
Appelbaum P, Grisso T. Assessing patients’ capacities to consent to treatment. N Engl J Med. 1988;319:1635–8.
Markson LJ, Kern DC, Annas GJ, Glantz LH. Physician assessment of patient competence. J Am Geriatr Soc. 1994;42:1074–80.
Fitten LJ, Lusky R, Hamann C. Assessing treatment decision-making capacity in elderly nursing home residents. J Am Geriatr Soc. 1990;38:1097–104.
Marson DC, McInturff B, Hawkins L, Bartolucci A, Harrell LE. Consistency of physician judgments of capacity to consent in mild Alzheimer’s disease. J Am Geriatr Soc. 1997;45:453–7.
Lo B. Assessing decision making capacity. Law Med Health Care. 1990;18:193–201.
Naglie G, Silberfeld M, O’Rourke K, et al. A randomized trial of a decisional aid for mental capacity assessments. J Clin Epidemiol. 1993;46:221–30.
Bean G, Nishisato S, Rector NA, Glancy G. The psychometric properties of the competency interview schedule. Can J Psychiatry. 1994;39:368–76.
Appelbaum PS, Mirkin SA, Bateman AL. Empirical assessment of competency to consent to psychiatric hospitalization. Am J Psychiatry. 1981;138:1170–6.
Grisso T, Appelbaum PS, Hill-Fotouhi C. The MacCAT-T: a clinical tool to assess patients’ capacities to make treatment decisions. Psychiatr Serv. 1997;48:1415–9.
Marson DC, Ingram KK, Cody HA, Harrell LE. Assessing the competency of patients with Alzheimer’s disease under different legal standards: a prototype instrument. Arch Neurol. 1995;52:949–54.
Fitten LJ, Waite MS. Impact of medical hospitalization on treatment decision-making capacity in the elderly. Arch Intern Med. 1990;150:1717–21.
Molloy DW, Silberfeld M, Darzins P, et al. Measuring capacity to complete an advance directive. J Am Geriatr Soc. 1996;44:660–4.
Mebane AH, Rauch HB. When do physicians request competency evaluations? Psychosomatics. 1990;31:40–6.
Etchells EE, Katz M, Shuchman M, et al. Accuracy of clinical impressions and mini mental status scores for assessing capacity to consent to treatment. Psychosomatics. 1997;38:239–45.
Grisso T, Appelbaum PS. Comparison of standards for assessing patients’ capacities to make treatment decisions. Am J Psychiatry. 1995;152:1033–7.
Molloy DW, Alemayehu E, Robert R. A Standardized Mini-Mental State Examination: its reliability compared to the traditional Mini-Mental State Examination. Am J Psychiatry. 1991;48:102–5.
Silberfeld M, Dickens BM, Harvey WRC, Pepper-Smith R. A competency clinic for the elderly at Baycrest Centre. Advocates Q. 1988;10(1):23–8.
Naglie G, Silberfeld M, O’Rourke K, et al. Convening expert panels to identify mental capacity assessment items. Can J Aging. 1995;14:697–705.
Silberfeld M, Finstad M, Stephens D. Agreement between professions on ethical decisions: an empirical demonstration. Int J Med Law. 1995;14(4):191–7.
Katz M, Abbey S, Rydall A, Lowy F. Psychiatric consultation for competency to refuse medical treatment. Psychosomatics. 1995;36:33–41.
Fleiss JL. Statistical method for Rates and Proportions. 2nd ed. New York, NY: J Wiley and Sons; 1981:212–25.
Hanley JA, McNeil BJ. A method for comparing the areas under the receiver operating characteristic curves derived from the same cases. Radiology. 1983;148:839–43.
Centor RM. Estimating confidence intervals of likelihood ratios. Med Decis Making. 1992;12:229–33.
Freedman M, Stuss DT, Gordon M. Assessment of competency: the role of neurobehavioural deficits. Ann Intern Med. 1991;115:203–8.
Morris CD, Niederbuhl JM, Mahr JM. Determining the capability of individuals with mental retardation to give informed consent. Am J Ment Retard. 1993;98:263–72.
Grisso T, Appelbaum PS, Mulvey EP, Fletcher K. The MacArthur Treatment Competence Study, II: measures of abilities related to competence to consent to treatment. Law Hum Behav. 1995;19:127–48.
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This project was supported by the physicians of Ontario through a grant (94–28) from Physicians’ Services Incorporated Foundation of Ontario. Dr. Naglie is partially supported by an Arthur Bond Fellowship from the Physicians’ Services Incorporated Foundation.
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Etchells, E., Darzins, P., Silberfeld, M. et al. Assessment of patient capacity to consent to treatment. J GEN INTERN MED 14, 27–34 (1999). https://doi.org/10.1046/j.1525-1497.1999.00277.x
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DOI: https://doi.org/10.1046/j.1525-1497.1999.00277.x