Neuropsychological correlates of capacity determinations in Alzheimer disease: implications for assessment

To explore the neuropsychological correlates of the capacity to consent to research and to appoint a research proxy among persons with Alzheimer disease.

Interview study of 77 persons with Alzheimer disease recruited through an Alzheimer disease research center and a memory disorder clinic.

The capacity to consent to two research scenarios (a drug randomized clinical trial and a neurosurgical clinical trial) and the capacity to appoint a research proxy were determined by five experienced consultation psychiatrists who rendered categorical judgments based on videotaped interviews of the MacArthur Competence Assessment Tool-Clinical Research and the Capacity to Appoint a Proxy Assessment. Mattis Dementia Rating Scale-Second Edition was used to assess neuropsychological functioning.

The capacity to appoint a proxy and to consent to the drug randomized clinical trial, as determined by a majority or greater opinion of the five-psychiatrist panel, was predicted by Conceptualization and Initiation/Perseveration subscales, whereas the capacity to consent to a neurosurgical randomized clinical trial was predicted by the Memory subscale. Furthermore, the more lenient individual psychiatrists' judgments were predicted by the Conceptualization subscale, whereas the stricter psychiatrists' judgments were predicted by the Memory subscale.

How experienced psychiatrists view the capacity of patients with Alzheimer disease for consenting to research and for appointing a proxy may be related to the patients' conceptualization and memory functioning. More explicit and standardized guidance on the role of short-term memory in capacity determinations may be useful.