Validation and modification of a Chinese smell identification test (CSIT-12) in patients with Parkinson's disease and rapid eye movement sleep behavior disorder

Background To enhance olfactory screening for Chinese patients with Parkinson's disease (PD) or rapid-eye movement sleep behavior disorder (RBD) by developing and modifying a Chinese Smell Identification Test 12 (CSIT-12). Methods In a discovery cohort, 69 PD patients and 47 healthy controls (HCs) were tested on 24 distinct odors using the Sniffin’ Sticks Screening Test 12 (SSST-12) and CSIT-12. The 12 odors with the highest area under the curve (AUC) were selected to construct the Chinese version of the Sniffin’ Sticks Screening Test 12 (C-SSST-12). This newly developed test was then validated in an independent cohort comprising 48 PD patients, 48 RBD patients, and 48 HCs. The reliability and validity of SSST-12, CSIT-12, C-SSST-12, and further abbreviated odor subsets were compared. Results Scores on SSST-12, CSIT-12, and C-SSST-12 were significantly lower in both PD and RBD compared to HCs (all P < 0.001). Both the CSIT-12 and SSST-12 demonstrated good discriminative capacity for PD versus HCs (CSIT-12: AUC = 0.832, sensitivity = 77.1%, specificity = 83.3%; SSST-12: AUC = 0.913, sensitivity = 85.4%, specificity = 81.3%) and RBD versus HCs (CSIT-12: AUC = 0.881, sensitivity = 85.4%, specificity = 83.3%; SSST-12: AUC = 0.893, sensitivity = 79.2%, specificity = 81.3%). Notably, the C-SSST-12 achieved the highest discriminative performance for PD versus HCs (AUC = 0.930, sensitivity = 81.3%, specificity = 85.4%) and RBD versus HCs (AUC = 0.949, sensitivity = 89.6%, specificity = 85.4%). A 5-odor CSIT-12 subset and a 3-odor C-SSST-12 subset retained high discriminative validity. Conclusions This study highlights the discriminative value of utilizing culturally familiar odors for the screening of PD and RBD in Chinese populations. Furthermore, the abbreviated odor subsets offer highly efficient, rapid screening options suitable for community-based testing and fast-paced clinical environments.