Odor identification in Alzheimer's disease and depression.

Background And Aims: In Alzheimer's disease (AD) olfactory deficits are common and depression is a difficult differential diagnosis. We therefore investigated the usefulness of an odor identification test to differentiate both conditions.

Methods: Twenty patients with probable Alzheimer's disease (AD), twenty elderly patients with a depressive disorder, and thirty healthy elderly subjects performed a German odor identification test.

Results: AD patients had significantly lower odor identification scores, compared with both depressive patients and control subjects (F=121.96, df=2, 67, p<0.001). With a cut-off score of 10/11, the sensitivity of the identification test to differentiate AD patients from depressive patients was 100%, and specificity was 95%.

Conclusions: The odor identification test used in this study is able to reveal olfactory deficits in AD. It also seems to be a useful instrument to differentiate AD from depression.