A re-evaluation study and literature review on AD8 as a screening tool for dementia

Abstract

Background: The Eight-Item Informant Interview to Differentiate Aging and Dementia (AD8) was developed as a screening tool for dementia, with a cutoff score of 2 suggested by the initial study. However, various studies have reported different cutoff values, and many have found that a cutoff of 2 may result in a high false positive rate. Furthermore, a high false positive rate has repeatedly been shown when the AD8 is self-administered in local government screening programs in Taiwan.

Objectives: This study aimed to test the AD8's performance, define its best cutoff value, review factors that may affect its performance, and reconsider its role in clinical practice.

Methods: We recruited 118 participant-informant dyads from a university teaching hospital. For each informant, the AD8 was administered before the Clinical Dementia Rating (CDR) to minimize recall bias. Two geriatric psychiatrists made a consensus clinical diagnosis for each participant based on the DSM-5 criteria. Receiver operating characteristic analysis was used to assess the performance of the AD8.

Results: Thirty-seven participants had a CDR of 0, 61 had a CDR of 0.5, and 20 had a CDR ≥ 1. To discriminate between the participants with CDR 0 and those with CDR 0.5, the optimal cutoff score for the AD8 was 2. Including those with CDR ≥ 1 changed the best cutoff value to 3. In terms of the DSM-5 criteria, 59 participants had normal cognition, 28 had mild neurocognitive disorder, and 31 had major neurocognitive disorder or dementia. To discriminate between those with and without dementia, an AD8 cutoff value of 4 maximized the Youden index with more balanced sensitivity and specificity.

Conclusion: The AD8 may have different cutoff values depending on different purposes. Our findings suggest that the AD8 may perform better with a cutoff value of 4 to discriminate between those with and without dementia.

Fig 1. Receiver operating characteristic curve for CDR 0 versus CDR 0.5.

The area under the curve was 0.800.

Fig 2. Receiver operating characteristic curve for CDR 0 versus CDR

≥ 0.5. The area under the curve was 0.844.

Fig 3. Receiver operating characteristic curve comparing the AD8 scores of the participants without and with dementia according to the DSM-5 diagnostic criteria.

The area under the curve was 0.893.