Slow Motion Analysis of Repetitive Tapping (SMART) test: measuring bradykinesia in recently diagnosed Parkinson’s disease and idiopathic anosmia

Background Bradykinesia is the defining motor feature of Parkinson’s disease (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. Objectives To develop a quantitative method to track repetitive finger tapping movements and to compare people in the early stages of PD, healthy controls, and individuals with idiopathic anosmia. Methods This was a cross-sectional study of 99 participants (early-stage PD=26, controls=64, idiopathic 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 section of MDS-UPDRS. 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. Conclusions 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The Preventive Neurology Unit is funded by the Barts Charity. AJN reports additional grants from Parkinson’s UK, Virginia Keiley benefaction, Aligning Science Across Parkinson's and Michael J Fox Foundation, and personal fees/honoraria from Britannia, BIAL, AbbVie, Global Kinetics Corporation, Profile, Biogen, Roche and UCB, outside of the submitted work. CS is funded by Fundacion Alfonso Martin Escudero, Spain. No other disclosures were reported. AL is funded by the Reta Lila Weston Institute of Neurological Studies, University College London, Institute of Neurology and reports consultancies/honoraria from Britannia Pharmaceuticals and BIAL Portela. He also reports grants and/or research support from the Frances and Renee Hock Fund. AS is supported by the NIHR UCL/H Biomedical Research Centre. CL is supported by an MRC Clinician Scientist award (MR/R006504/1). The Wellcome Centre for Human Neuroimaging is supported by core funding from the Wellcome Trust (203147/Z/16/Z). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. The authors confirm that all participants gave verbal and written consent for this work. Ethics approval was granted by the PREDICT-PD study was approved by Central London Research Committee 3 (reference number 10/H0716/85). The qMAP-PD study has full NHS ethical approval (Fulham Research Ethics Committee, 18/LO/1229). All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.