Evaluation of cognitive impairment in older adults: combining brief informant and performance measures

Abstract

Objective: To combine the AD8, a brief informant interview, with performance measures to develop a brief screening tool to improve detection of cognitive impairment and dementia in general practice.

Design: The AD8 was administered to informants. Clinicians conducted independent patient evaluations and administered the Clinical Dementia Rating Scale and a 30-minute neuropsychological battery. Logistic regression was used to determine the best combination of brief tests to correctly classify patients as having no dementia, uncertain dementia, or dementia. The area under the receiver operator characteristic curve (AUC) evaluated the discriminative ability of the combined tests.

Patients/setting: Patients (n = 255) were consecutive referrals to a dementia clinic. Patients had a mean +/- SD age of 73.3 +/- 11.3 years, with 13.7 +/- 3.0 (mean +/- SD) years of education. The sample was 56% women; 77% of patients were white. Main Outcome Measure Dementia classification.

Results: A model combining the AD8 interview (odds ratio, 1.91; 95% confidence interval, 1.6-2.3) and the Consortium to Establish a Registry for Alzheimer Disease 10-item Word List Recall (odds ratio, 1.43; 95% confidence interval, 1.2-1.7) predicted dementia with 91.5% correct classification (AUC = 0.968; 95% confidence interval, 0.93-0.99). A cutoff of 2 or greater on the AD8 and less than 5 items remembered on the Word List Recall was sensitive (94%) and specific (82%). For cognitive impairments not meeting dementia criteria, combining AD8 (odds ratio, 2.31; 95% confidence interval, 1.3-4.0) and Word List Recall (odds ratio, 1.42; 95% confidence interval, 1.1-1.8) was most predictive (AUC = 0.91; 95% confidence interval, 0.8-1.0). Using the same cutoffs as those used for dementia gave the best combination of sensitivity (85%) and specificity (84%).

Conclusion: Combining the AD8 interview with the Word List Recall improves the ability to detect the presence of dementia. The AD8 can be administered to an informant and, when combined with Word List Recall, is a powerful yet brief method of detecting cognitive impairment.