Objective: To develop a quantitative method to track repetitive finger tapping movements and to compare people in the early stages of Parkinson’s disease (PD), healthy controls, and individuals with idiopathic anosmia.

Background: Bradykinesia is the defining motor feature of PD. There are limitations to its assessment using standard clinical rating scales, especially in the early stages of PD when a floor effect may be observed.

Method: This was a cross-sectional study of 99 participants (early-stage PD=26, controls=64, anosmia=9). For each participant, repetitive finger tapping was recorded over 20 seconds using a smartphone at 240 frames per second. Three parameters were extracted from videos: amplitude between fingers, frequency (number of taps per second), and velocity (distance travelled per second). Clinical assessment was based on the motor score of Unified PD Rating Scale (MDS-UPDRS-III).

Results: People in the early stage of PD performed the task with slower velocity (p<0.001) and with greater decrement in frequency than controls (p=0.003). The combination of slower velocity and greater decrement in frequency obtained the best accuracy to separate early-stage PD from controls based on metric thresholds alone (AUC = 0.88). Individuals with anosmia exhibited slower velocity (p=0.001) and smaller amplitude (p<0.001) compared with controls.

Conclusion: We present a new simple method to detect early motor dysfunction in PD. Mean tap velocity appeared to be the best parameter to differentiate patients with PD from controls. Patients with anosmia also showed detectable differences in motor performance compared with controls which may be important indication of the prodromal phase of PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/slow-motion-analysis-of-repetitive-tapping-smart-test-measuring-of-bradykinesia-in-recently-diagnosed-parkinsons-disease-and-idiopathic-anosmia/