Evaluation of olfactory impairment using a simple test kit “The Odor Stick Identification test for the Japanese” (OSIT-J) in neurodegenerative diseases

Purpose: Olfactory deficit has been studied in aging, amnestic mild cognitive impairment (aMCI), Alzheimer’s disease (AD). Parkinson\u27s disease (PD), dementia with Lewy bodies (DLB) and idiopathic REM-sleep behavior disorder (iRBD). Our aim was to investigate the usefulness of a simple test kit “The Odor Stick Identification test for the Japanese ”(OSIT-J) in clinical practice.Methods: A total of 240 patients were enrolled in this study, including 44 cognitively normal subjects (NS), 31 patients with aMCI, 70 patients with mild AD (AD-mild), 28 patients with DLB, 31 patients with PD and 36 patients with iRBD. The OSIT-J consists of 12 types of odor sticks. The subjects were asked to select an odor from a list of 4 odors that were rubbed on the medicine wraping paper for each odor stick. The maximum score was 12.Results: The mean odor identification (OI) score decreased in the order of aMCI, iRBD, AD-mild, PD and DLB (NS: aMCI, P<0.05, NS: AD-mild, DLB, PD and iRBD, P<0.001, aMCI: DLB, P<0.001, aMCI: PD, P<0.01 (Kruskal-Wallis, Dunn’s test). The sensitivity and specificity in differentiating each disease from NS at a cutoff value of 8 was 96.8% and 79.5%, respectively, in PD, and 96.4% and 79.5% in DLB. An ageing effect was observed in NSs ( r=-0.453 (p<0.01)).Conclusions: Olfactory deficit is a non-specific phenomenon. However, it is important to be aware of the underlying diseases or future development of diseases. The OSIT-J, which is a simple test, is useful for detecting OI abnormalities in daily clinical practice