The assessment of functional capacity is essential for the diagnosis of dementia by DSM-IV criteria and has important implications for patient intervention and management. Although ratings of functional disability by family or other proxy informants are widely used by clinicians, there have been concerns and empirical evidence that potential reporter biases may result in either overestimation or underestimation of specific functional deficits. In this study, we compared family members' judgments of the functional abilities of seventy-two patients diagnosed with Alzheimer's disease (AD). These judgments were compared to actual objective functional performance on an array of real-world tasks using the Direct Assessment of Functional Status (DAFS) scale. The results indicate that caregivers were extremely accurate in predicting the functional performance of AD patients who were not impaired during objective evaluation. In contrast, caregivers significantly overestimated the ability of impaired AD patients to tell time, to identify currency, to make change for a purchase, and to utilize eating utensils. Higher patient MMSE scores were associated with caregivers' overestimation of functional capacity, while the degree of caregivers' depressive symptoms, as measured by the CES-D depression scale, was not related to either overestimation or underestimation of patients' functional performance.

Visuoconstructional ability was assessed by asking patients diagnosed with Alzheimer's disease (AD), ischaemic vascular dementia (IVD), and Parkinson's disease (PD) and a normal control group (NC) to copy a modification of the Rey-Osterrieth Complex Figure (M-ROCF). The drawings of the NC group were superior to all dementia participants. AD patients generally outperformed IVD and PD patients; however, there were few differences between IVD and PD groups. Nonetheless, the drawings of IVD and PD patients were very fragmented and contained numerous perseverations and omissions. Despite these errors, patients with IVD and PD obtained higher delayed recognition memory scores than AD patients. Correlational analyses among dementia patients between neuropsychological tests and the copy of the M-ROCF found that accurate figure copy was most consistently correlated with tests of working memory, that is, tests requiring patients to monitor their behavior and sustain a complex mental set while performing mental manipulations. By contrast, no relationship between executive function tests related to measures of response selection/inhibition or other domains of neuropsychological functioning was found.

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