Toward a neurologic model of competency: Cognitive predictors of capacity to consent in Alzheimer's disease using three different legal standards.

OBJECTIVE: To identify cognitive predictors of competency performance and status in Alzheimer's disease (AD) using three differentially stringent legal standards for capacity to consent. DESIGN: Univariate and multivariate analyses of independent neuropsychological test measures with three dependent measures of competency to consent to treatment. SETTING: University medical center. SUBJECTS: 15 normal older controls and 29 patients with probably AD (15 mild and 14 moderate). MAIN OUTCOME MEASURES: Subjects were administered a batter of neuropsychological measures theoretically linked to competency function, as well as two clinical vignettes testing capacity to consent to medical treatment under five legal standards (LSs). The present study focused on three differentially stringent LSs: the capacity simply to "evidence a treatment of choice" (LS1), which is a minimal standard; the capacity to "appreciate the consequences" of a treatment of choice (LS3), a moderately stringent standard; and the capacity to "understand the treatment situation and choices" (LS5), the most stringent standard. Control subject and AD patient neuropsychological test scores were correlated with scores on the three LSs. The resulting univariate correlates were than analyzed using stepwise regression and discriminant function to identify key multivariate predictors of competency performance and status under each LS. RESULTS: No neuropsychological measures predicted control group performance on the LSs. For the AD group, a measure of simple auditory comprehension predicted LS1 performance (r(2)=0.44, p < 0.0001), a word fluency measure predicted LS3 performance (r(2)=0.58, p < 0.0001), and measures of conceptualization and confrontation naming together predicted LS5 performance (r(2)=0.81, p < 0.0001). Under discriminant function analysis, confrontation naming was the best single predictor of LS1 competency status for all subjects, correctly classifying 96% of cases (42/44). Measures of visumotor tracking and confrontation naming were the best single predictors, respectively, of competency status under LS3 (91% [39/43]) and LS5 (98% [43/44]). CONCLUSIONS: Multiple cognitive functions are associated with loss of competency in AD. Deficits in conceptualization, semantic memory, and probably verbal recall are associated with the declining capacity of mild AD patients to understand a treatment situation and choices (LS5); executive dysfunction with the declining capacity of mild to moderate AD patients to identify the consequences of treatment choice (LS3); and receptive aphasia and severe dysnomia with the declining capacity of advanced AD patients to evidence a simple treatment choice (LS1). The results offer insight into the relationship between different legal thresholds of competency and the progressive cognitive changes characteristic of AD, and represent an initial step toward a neurologic model of competency.

Assessing the competency of patients with Alzheimer's disease under different legal standards. A prototype instrument.

OBJECTIVE: To assess empirically the competency of patients with Alzheimer's disease (AD) to consent to medical treatment under different legal standards (LSs). DESIGN: Comparison of normal older subjects and patients with AD on measures of competency to consent to medical treatment. SETTING: University medical center. SUBJECTS: Normal older control subjects (n = 15) and patients with probable AD (n = 29 [15 with mild and 14 with moderate AD]). MAIN OUTCOME MEASURES: Two specialized clinical vignettes were developed that test a subject's capacity to consent to medical treatment under five well-established LSs for this competency: LS1, evidencing treatment choice; LS2, making the reasonable choice; LS3, appreciating consequences of choice; LS4, providing rational reasons for choice; and LS5, understanding treatment situation and choices. Performance on the LSs was compared across control and AD groups using Student's t test, chi 2, and analysis of variance. Demented subjects were categorized as competent, marginally competent, or incompetent under each LS by using a cutoff score derived from normal control performance. RESULTS: No differences between groups emerged for LS1 and LS2. Control subjects performed significantly better than patients with mild AD on LS4 and LS5, and significantly better than patients with moderate AD on LS3, LS4, and LS5. Patients with mild AD performed significantly better than patients with moderate AD on LS4 and LS5. With respect to competency status, patients with AD showed a consistent and progressive pattern of compromise (marginal competence or incompetence) related to dementia severity and stringency of the LS. CONCLUSIONS: A reliable prototype instrument validly discriminated the competency performance and classified the competency status of control subjects and patients with mild and moderate AD under five LSs for competency to consent to medical treatment. While the groups performed equivalently on minimal standards requiring merely a treatment choice (LS1) or the reasonable treatment choice (LS2), patients with mild AD had difficulty with more difficult standards requiring rational reasons (LS4) and understanding treatment information (LS5), and patients with moderate AD had difficulty with appreciation of consequences (LS3), rational reasons (LS4), and understanding treatment (LS5). The results raised the concern that many patients with mild AD may not be competent to consent to treatment and supported the value of standardized clinical vignettes for assessment of competency in dementia.

Neuropsychologic predictors of competency in Alzheimer's disease using a rational reasons legal standard.

OBJECTIVE: To identify neuropsychologic predictors of competency performance and status in Alzheimer's disease (AD) using a specific legal standard (LS). This study is a follow-up to the competency assessment research reported in this issue of the archives. DESIGN: Univariate and multivariate analyses of independent neuropsychologic test measures with a dependent measure of competency to consent to treatment. SETTING: University medical center. SUBJECTS: Fifteen normal older control subjects and 29 patients with probable AD. MAIN OUTCOME MEASURES: Subjects were administered a battery of neuropsychologic measures theoretically linked to competency function, as well as two clinical vignettes testing their capacity to consent to medical treatment under five different LSs. The present study focused on one specific LS: the capacity to provide "rational reasons" for a treatment choice (LS4). Neuropsychologic test scores were correlated with scores on LS4 for the normal control group and the AD group. The resulting univariate predictors were then analyzed using stepwise regression and discriminant function to identify the key multivariate predictors of competency performance and status under LS4. RESULTS: Measures of word fluency predicted the LS4 scores of controls (R2 = .33) and the AD group (R2 = .36). A word fluency measure also emerged as the best single predictor of competency status for the full subject sample (n = 44), correctly classifying 82% of cases. Dementia severity (Mini-Mental State Examination score) did not emerge as a multivariate predictor of competency performance or status. Interestingly, measures of verbal reasoning and memory were not strongly associated with LS4. CONCLUSIONS: Word fluency measures predicted the normative performance and intact competency status of older control subjects and the declining performance and compromised competency status of patients with AD on a "rational reasons" standard of competency to consent to treatment. Cognitive capacities related to frontal lobe function appear to underlie the capacity to formulate rational reasons for a treatment choice. Neuropsychologic studies of competency function have important theoretical and clinical value.

Determining the competency of Alzheimer patients to consent to treatment and research.

Loss of competency is an inevitable consequence of Alzheimer disease (AD) and other progressive dementias. Of particular importance to clinicians and researchers studying dementia is determining whether a patient has the capacity to provide informed consent to treatment and medical research. No widely accepted standardized instruments exist for competency assessment, nor has competency assessment training been available to physicians. As a result, physician competency assessment has been a subjective and even idiosyncratic process. Recent studies have suggested that physicians have difficulty assessing capacity to consent in older adults and frequently disagree in their competency judgments. Accordingly, one important goal for advancing ethical and legal research in AD will involve the development of standardized approaches to determining patient capacity to give consent. This article reports the findings of recent empirical studies of competency determination in AD, focusing on work in the areas of physician competency assessment, development of standardized assessment instruments, and neuropsychological modeling of competency loss. Future directions for research in these three areas are identified.