Use of the Brief Smell Identification Test for olfactory deficit in a Norwegian population with Alzheimer's disease

Abstract

Several studies have shown that Alzheimer's disease (AD) is associated with hyposmia. Olfactory identification may be a cheap and simple additional test in the assessment of early cognitive changes. The sense of smell is influenced by factors such as experience and culture and the aim of the present study was to assess the validity of the Brief Smell Identification Test (B-SIT) in distinguishing patients with AD from healthy gender and age-matched controls in a Norwegian population. The study included 39 patients with a diagnosis of probable AD, and 52 gender and age-matched controls. Olfactory function was assessed with B-SIT, and a non-standardized olfactory identification task (freshly ground coffee). The difference in olfactory performance between patients and controls was highly significant, both for the whole AD patient group and the subgroup of patients with MMSE >or= 24. Receiver operating curve (ROC) analyses indicated that B-SIT distinguished patients from controls with high sensitivity and specificity. All the odours in B-SIT with the exception of turpentine showed highly significant differences between patients and controls. AD-associated memory impairment did not seem to affect the answers given for B-SIT in this population. For patients with AD, the Brief Smell Identification Test (B-SIT) appears to be well-suited for detecting a deficit in olfactory identification in a Norwegian population.