Olfactory dysfunction in incidental Lewy body disease and Parkinson's disease

Background: Olfactory dysfunction in Parkinson's disease (PD) is well-established and may represent one of the earliest signs of the disease. Objective & methods: The objective of this study was to evaluate the relationship of olfactory dysfunction, using the University of Pennsylvania Smell Identification Test (UPSIT), to clinical and pathological parameters of clinicopathologically diagnosed PD (n=10), incidental Lewy body disease (ILBD) (n=13), and identically assessed controls who lacked a neurodegenerative disease (n=69). Results: Mean UPSIT scores were significantly lower in PD (16.3, p<0.001) and ILBD (22.2, p=0.004) compared to controls (27.7). Using an UPSIT cutoff score of <22 (the 15th percentile) the sensitivity for detecting PD was 9/10 (90%) and ILBD 6/13 (46%), while the specificity was 86% (Controls with score of <22=10/69). Conclusions: These results add to the growing body of evidence suggesting that olfactory testing could be useful as a screening tool for identifying early, pre-motor PD.