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BACKGROUND: Dementia patients with anosmia are more likely to have Lewy body pathology at postmortem, but clinicopathological studies have only assessed olfaction in moderate dementia or an average of 5 years before death. It is not known whether, in patients with mild dementia (MMSE score over 20), olfactory function is more impaired in Alzheimer disease (AD) than dementia with Lewy bodies (DLB). METHODS: Patients with mild DLB (n = 21), mild AD (n = 27), mild cognitive impairment (MCI) (n = 21) and controls (n = 47) were assessed using a 16-item olfactory identification test and an olfactory threshold test which used sticks impregnated with differing concentrations of butanol. RESULTS: Patients with mild DLB had impaired olfactory identification ability compared with those with mild AD or MCI, independent of age, cognitive function and sex. The sensitivity of a cutoff score of seven correct responses out of 16 was 0.81 for distinguishing mild DLB from mild AD (AUC 0.682). The specificity, positive predictive value and negative predictive value for the same cut-off score were 0.41, 0.48 and 0.73, respectively. The olfactory threshold was not different in the AD and DLB groups. CONCLUSIONS: Simple bedside tests of olfactory identification merit further examination for their potential to improve the identification of patients with DLB when used alongside existing criteria. They are insufficiently specific for use in screening.

Original publication

DOI

10.1136/jnnp.2008.155895

Type

Journal article

Journal

J Neurol Neurosurg Psychiatry

Publication Date

06/2009

Volume

80

Pages

667 - 670

Keywords

Aged, Aged, 80 and over, Alzheimer Disease, Cognition Disorders, Diagnosis, Differential, Female, Humans, Lewy Body Disease, Male, Mental Status Schedule, Olfaction Disorders, Point-of-Care Systems, ROC Curve, Sensory Thresholds