Patient's rating of cognitive ability: using the AD8, a brief informant interview, as a self-rating tool to detect dementia.

OBJECTIVE: To test the ability of patients to rate their own cognitive ability using the AD8 compared with informant and clinician ratings of cognitive status. DESIGN, SETTING, AND PATIENTS: The AD8 was administered to 325 consecutive participant-informant dyads enrolled in a longitudinal study at Washington University School of Medicine between April 4, 2005, and December 15, 2005. The number of AD8 items endorsed by the participant was compared with informant answers and an independently derived Clinical Dementia Rating. MAIN OUTCOME MEASURE: Strength of association was measured with Spearman (rho) and intraclass correlation coefficients. Receiver operator characteristic curves assessed the discriminative properties of the AD8.
RESULTS: The mean age of participants and informants was 72.8 years (range, 43-104 years) and 66.4 years (range, 24-101 years), respectively. The Clinical Dementia Rating was correlated with both informant (rho = 0.75, P<.001) and participant (rho = 0.34, P<.001) AD8 scores. Participants' AD8 scores had adequate agreement with informants' AD8 scores (intraclass correlation coefficient, 0.53; 95% confidence interval, 0.41-0.62) and correlated with subjective complaints of memory problems (rho = 0.47, P<.001) but not with estimates of symptom duration. The area under the receiver operator characteristic curve for the informant AD8 was 0.89 (95% confidence interval, 0.86-0.93); for the participant AD8, it was 0.78 (95% confidence interval, 0.68-0.78).
CONCLUSIONS: The AD8 is a brief measure that, when completed by an informant, differentiates nondemented from demented individuals. We now demonstrate that a self-completed AD8 also differentiates nondemented from demented individuals, although the utility was better in mildly impaired individuals compared with more demented individuals. In the absence of a reliable informant, the AD8 may be asked of the participant to gain an understanding of their perception of cognitive status.