Odor‐Specific Symptoms in Parkinson’s Disease—UPSIT‐TC Odor Identification Status Versus Clinical Severity

Olfactory dysfunction is a well‐recognized prodromal sign of Parkinson’s disease (PD). This study aimed to explore the potential of short‐form olfactory tests as a more convenient method for assessing PD symptoms in clinical practice. This retrospective cross‐sectional study included 176 patients with PD. For each clinical measure, 40 separate logistic regression models evaluated its association with correct identification of each UPSIT‐TC odor. Odors showing nominal associations at unrounded p < 0.05 were designated candidate symptom‐associated odors. A symptom‐specific odor score was constructed when at least two odors (≥ 2) met this criterion. Associations of each clinical measure with the UPSIT‐TC total score and its corresponding symptom‐specific odor score were subsequently evaluated using correlation analyses and covariate‐adjusted regression models. Across all clinical measures, 101 nominal odor–clinical associations involving 31 unique odors were identified, with 17 clinical measures meeting the ≥ 2‐odor criterion. Symptom‐specific odor scores generally showed stronger unadjusted correlations with their corresponding clinical measures than did the UPSIT‐TC total score. After adjustment for age, sex, disease duration, and levodopa equivalent daily dose (LEDD), with false discovery rate correction across 32 models, symptom‐specific odor scores remained significantly associated with MDS‐UPDRS total and Parts I–III scores, bradykinesia, rigidity, axial symptoms, NMSS total and gastrointestinal and urinary domain scores, MoCA scores, and NPI total scores. In contrast, the UPSIT‐TC total score remained significantly associated only with rigidity. Symptom‐specific odor scores have the potential to serve as a more clinically practical tool for assessing PD symptom burden than the UPSIT‐TC total score. Further large‐scale, multicenter studies are needed to explore odors with higher specificity for PD clinical symptoms.