Accurate detection of Parkinson's disease in tremor syndromes using olfactory testing.
OBJECTIVE
The diagnostic value of olfactory testing for the discrimination of tremor-dominant Parkinson's disease (PD) from other tremor disorders remains enigmatic. We evaluated whether olfactory testing can accurately detect PD in tremor patients.


METHODS
A retrospective analysis of 299 consecutive subjects referred for the differential diagnosis of a tremor disorder was done. Olfactory testing was performed using 'Sniffin' Sticks', resulting in a composite TDI score of odor threshold (T), discrimination (D), and identification (I). Receiver operating curve (ROC) plots were used to calculate sensitivity/specificity for the detection of PD.


RESULTS
Of all subjects, 167 (55.9%) had PD and 85 (28.4%) had essential tremor (ET). The mean TDI score in PD was significantly reduced compared to those in ET and other tremor disorders with no differences between ET and other tremor disorders. ROC analysis revealed strong correlations of TDI scores with PD [area under the curve: 0.85 (95% CI: 0.80-0.89); p < 0.001]. The highest Youden index was observed for a TDI score <25 (Youden index: 0.58). Using this cutoff score and that generated from normative data of healthy controls, the TDI score provided high sensitivity (negative predictive value) and specificity (positive predictive value) of approximately 80% for detecting PD.


CONCLUSIONS
Olfactory testing is a useful, easily applied and inexpensive diagnostic test which is helpful to detect PD among tremor patients.
Division of Neurodegenerative Diseases, Department of Neurology, Dresden University of Technology, Dresden, Germany.
Martin
M
Wolz
Antje
A
Hähner
Linda
L
Meixner
Matthias
M
Löhle
Heinz
H
Reichmann
Thomas
T
Hummel
Alexander
A
Storch
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D003937:Diagnosis, Differential; D004192:Discrimination, Psychological; D020329:Essential Tremor / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009812:Odorants; D055696:Olfactory Perception; D010300:Parkinson Disease / Q000175:diagnosis* / Q000503:physiopathology; D010812:Physical Stimulation; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012684:Sensory Thresholds; D014202:Tremor / Q000175:diagnosis* / Q000503:physiopathology; D055815:Young Adult