Developing and Validating a New Web-Based Tapping Test for Measuring Distal Bradykinesia in Parkinson’s Disease

ABSTRACTBackgroundDisability in Parkinson’s disease (PD) is measured by standardised scales including the MDS-UPDRS, which are subject to high inter and intra-rater variability and fail to capture subtle motor impairment. The BRadykinesia Akinesia INcoordination (BRAIN) test is a previously validated keyboard tapping test, evaluating proximal upper-limb motor impairment. Here, a new Distal Bradykinesia Tapping (DBT) test was developed to assess distal upper-limb function. Kinetic parameters of the test include kinesia score (KS20, key taps over 20 seconds), akinesia time (AT20, mean dwell-time on each key) and incoordination score (IS20, variance of travelling time between key taps).ObjectiveTo develop and validate a new keyboard-tapping test to assess distal motor function in PD patients.MethodsThe DBT test was validated in 45 PD patients and 24 controls, alongside the BRAIN test. Test scores were compared between groups and correlated with MDS-UPDRS-III scores. 10 additional PD patients were recruited to assess the DBT test in monitoring motor fluctuations.ResultsAll three parameters discriminated between patients and controls, with KS20 performing best, yielding 75% sensitivity for 85% specificity; area under the receiver operating characteristic curve (AUC) = 0.87. Combination of both the DBT and BRAIN tests improved discrimination (AUC=0.91). KS20 and AT20 correlated with MDS-UPDRS-III (Pearson’s r=-0.49, p<0.001 and r=0.54, p<0.001, respectively). The DBT test detected subtle changes in motor fluctuation states, which were not reflected clearly by MDS-UPDRS-III sub-scores.ConclusionThe DBT test is a user-friendly method of assessing distal motor dysfunction in PD, possibly permitting longitudinal monitoring of PD motor complications.