Application of odor identification test in Parkinson's disease in China: a matched case-control study

As one of the most common non-motor symptoms in Parkinson's disease (PD), hyposmia is of great importance in establishing the early diagnosis of PD. To date, there are still no studies on the application of the 16-item odor identification test from Sniffin' Sticks (SS-16) in Chinese patients with PD. The aim of this study was to investigate the validity of SS-16 in Chinese PD patients (n=110) compared with age and gender matched controls (n=110), and to explore the associated factors with olfactory function in PD patients. The 16 odors in the original odor identification test were retained but some alternative descriptions were developed before applications. Mean identification scores in patients were significantly lower than in controls (7.3 ± 2.8 VS. 11.6 ± 2.0 P<0.01), with 66.4% of patients had an impairment of odor identification as evaluated by 95% confidential interval of the identification score of the control group. Receiver operating characteristic curves revealed 86% sensitivity and 81% specificity in separating PD and healthy controls with a cut-off value of 9.5. Multiple linear regression analysis revealed that autonomic dysfunction was a significant influential factor of odor identification scores in patients with PD. In conclusion, SS-16 provides a valid instrument for olfactory assessment in Chinese PD patients, and hyposmia may correlate with autonomic dysfunction in patients with PD.