AD8 cut-offs of 2 and 4 now separate MCI from dementia when patients cannot be tested

Design

Cross-sectional psychometric linking study

Population

264 hospitalised older adults and their proxies

Primary outcome

Equivalent AD8 scores for IQCODE MCI and dementia cut-offs

Effect

AD8 2 ≈ IQCODE 3.2 (MCI); AD8 4 ≈ IQCODE 3.5 (dementia)

This study, published 24 September in the Journal of the American Geriatrics Society, gave both the 16-item IQCODE and the 8-item AD8 to proxies of 264 hospitalised older adults (mean age 79.5), then linked the two scores using equipercentile and item response theory methods.

An AD8 score of 2 corresponded to an IQCODE of 3.2, the cut-off for mild cognitive impairment. An AD8 score of 4 corresponded to an IQCODE of 3.5, the cut-off for dementia. Until now, the AD8 had a single cut-off for "cognitive impairment".

In a delirious inpatient, direct cognitive testing tells you about the delirium, not the brain underneath. A short informant interview with the family, with these two thresholds, gives a usable estimate of baseline cognition in a couple of minutes.

• Use an informant questionnaire to estimate baseline cognition in delirious older inpatients.
• An AD8 score of 2 or more suggests mild cognitive impairment.
• An AD8 score of 4 or more suggests dementia.
• Confirm with formal assessment once the delirium has resolved.

Why it matters

Lets clinicians separate pre-existing cognitive impairment from delirium in the first hours of admission.

Don't overread it

Cut-offs were derived by linking to another questionnaire, not validated against clinical diagnosis, in one US hospital population.

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