Validity and reliability of the AD8 informant interview in dementia.
OBJECTIVE
To establish the validity, reliability, and discriminative properties of the AD8, a brief informant interview to detect dementia, in a clinic sample.


METHODS
We evaluated 255 patient-informant dyads. We compared the number of endorsed AD8 items with an independently derived Clinical Dementia Rating (CDR) and with performance on neuropsychological tests. Construct and concurrent validity, test-retest, interrater and intermodal reliability, and internal consistency of the AD8 were determined. Receiver operator characteristic curves were used to assess the discriminative properties of the AD8.


RESULTS
Concurrent validity was strong with AD8 scores correlating with the CDR (r = 0.75, 95% CI 0.63 to 0.88). Construct validity testing showed strong correlation between AD8 scores, CDR domains, and performance on neuropsychological tests. The Cronbach alpha of the AD8 was 0.84 (95% CI 0.80 to 0.87), suggesting excellent internal consistency. The AD8 demonstrated good intrarater reliability and stability (weighted kappa = 0.67, 95% CI 0.59 to 0.75). Both in-person and phone administration showed equal reliability (weighted kappa = 0.65, 95% CI 0.57 to 0.73). Interrater reliability was very good (Intraclass correlation coefficient = 0.80, 95% CI 0.55 to 0.92). The area under the curve was 0.92 (95% CI 0.88 to 0.95), suggesting excellent discrimination between nondemented individuals and those with cognitive impairment regardless of etiology.


CONCLUSIONS
The AD8 is a brief, sensitive measure that validly and reliably differentiates between nondemented and demented individuals. It can be used as a general screening device to detect cognitive change regardless of etiology and with different types of informants.
Galvin
James E
JE
Departments of Neurology, Alzheimer Disease Research Center, Washington University School of Medicine, 4488 Forest Park, Suite 130, St. Louis, MO 63108, USA. galvinj@neuro.wustl.edu
Roe
Catherine M
CM
Xiong
Chengjie
C
Morris
John C
JC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003704:Dementia / Q000175:diagnosis* / Q000523:psychology; D005260:Female; D006801:Humans; D007407:Interviews as Topic / Q000379:methods / Q000592:standards*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000592:standards*; D012680:Sensitivity and Specificity