The BRadykinesia Akinesia INcoordination (BRAIN) Tap Test: Capturing the Sequence Effect

Abstract

Background: The BRadykinesia Akinesia INcoordination (BRAIN) tap test is an online keyboard tapping task that has been previously validated to assess upper limb motor function in Parkinson's disease (PD).

Objectives: To develop a new parameter that detects a sequence effect and to reliably distinguish between PD patients on and off medication. In addition, we sought to validate a mobile version of the test for use on smartphones and tablet devices.

Methods: The BRAIN test scores in 61 patients with PD and 93 healthy controls were compared. A range of established parameters captured number and accuracy of alternate taps. The new velocity score recorded the intertap speed. Decrement in the velocity score was used as a marker for the sequence effect. In the validation phase, 19 PD patients and 19 controls were tested using different hardware including mobile devices.

Results: Quantified slopes from the velocity score demonstrated bradykinesia (sequence effect) in PD patients (slope cut-off -0.002) with 58% sensitivity and 81% specificity (discovery phase of the study) and 65% sensitivity and 88% specificity (validation phase). All BRAIN test parameters differentiated between on and off medication states in PD. Differentiation between PD patients and controls was possible on all hardware versions of the test.

Conclusion: The BRAIN tap test is a simple, user-friendly, and free-to-use tool for the assessment of upper limb motor dysfunction in PD, which now includes a measure of bradykinesia.

Keywords: Parkinson's disease; ambulatory monitoring; digital health; hypokinesia; objective measures.

Conflict of interest statement

The work presented here had no specific funding, but the Preventive Neurology Unit is funded by the Barts Charity and the Exenatide PD study was funded by the Michael J. Fox Foundation and the Cure Parkinson's Trust. A.J.N. was funded by Parkinson's UK at the time the data were collected and M.B. by the Reta Lila Weston Trust. B.H. and B.J. are directors of uMotif Limited. H.H., M.B., D.S.A., T.W., T.F., G.G., A.J.L., and A.J.N. report no relevant disclosures or conflicts of interest.

Figures

Figure 1

Time‐series analysis of change in velocity for the duration of the test compared to the initial velocity in a patient with Parkinson's disease (PD; left) and healthy control (right). The slope was derived from the regression equation of the linear trendline.

Figure 2

Box‐and‐whisker plot comparing the most‐affected side in patients with Parkinson's disease (PD) in the OFF state with the nondominant side in controls: (A) the first experiment (P < 0.001), (B) the third experiment (P < 0.001).

Figure 3

Comparison of KS, AT, IS, and VS (A–D, respectively) between patients with Parkinson's disease (PD) off medication (n = 61) and controls in the first and second experiments (n = 93 for KS, AT, IS and n = 40 for VS) using receiver operating characteristic curves (worse‐affected side in PD was compared to the lowest score of the 2 hands in controls). KS, kinesia score; AT, akinesia time; IS, incoordination score; VS, velocity score; AUC, area under the curve.

Figure 4

Correlation of ∑KS and ∑VS with total Movement Disorders Society–Unified Parkinson's Disease Rating Scale motor scores in patients (n = 60) off medication (A and C, respectively) and on medication (B and D, respectively). ∑KS, average KS scores for both hands off medication; ∑VS, average VS scores for both hands off medication; T.UPDRS, total motor Unified Parkinson's Disease Rating Scale scores.