Developing and assessing a new web-based tapping test for measuring distal movement in Parkinson's disease: a Distal Finger Tapping test

Abstract

Disability 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 validated keyboard tapping test, evaluating proximal upper-limb motor impairment. Here, a new Distal Finger Tapping (DFT) test was developed to assess distal upper-limb function. Kinetic parameters of the test include kinesia score (KS20, key taps over 20 s), akinesia time (AT20, mean dwell-time on each key) and incoordination score (IS20, variance of travelling time between key taps). To develop and evaluate a new keyboard-tapping test for objective and remote distal motor function in PD patients. The DFT and BRAIN tests were assessed in 55 PD patients and 65 controls. Test scores were compared between groups and correlated with the MDS-UPDRS-III finger tapping sub-scores. Nine additional PD patients were recruited for monitoring motor fluctuations. All three parameters discriminated effectively between PD patients and controls, with KS20 performing best, yielding 79% sensitivity for 85% specificity; area under the receiver operating characteristic curve (AUC) = 0.90. A combination of DFT and BRAIN tests improved discrimination (AUC = 0.95). Among three parameters, KS20 showed a moderate correlation with the MDS-UPDRS finger-tapping sub-score (Pearson's r = - 0.40, p = 0.002). Further, the DFT test detected subtle changes in motor fluctuation states which were not reflected clearly by the MDS-UPDRS-III finger tapping sub-scores. The DFT test is an online tool for assessing distal movements in PD, with future scope for longitudinal monitoring of motor complications.

Figure 1

Comparison of the BRAIN test and DFT test. Left: BRAIN test, alternate tapping of the ‘s’ and ‘;’ keys with the index finger and online interface below. Right: DFT test, repeated tapping of down arrow key with left index finger whilst depressing the left arrow key with left middle finger and online interface below.

Figure 2

Comparison of KS20, AT20 and IS20 in PD patients and controls. Spread of (a) KS20, (b) AT20 (mean and SD) and (c) IS20 (median and IQR) for patients and controls. Receiver operating curves for (d) KS20, (e) AT20 and (f) IS20.

Figure 3

Correlation between DFT parameters and MDS-UPDRS-III finger tapping sub-socres. (a) Moderate negative correlation with KS20 and UPDRS. (b) Moderate positive correlation seen with AT20 and finger tapping sub-score. (c) No correlation seen with IS20 and finger tapping sub-score.

Figure 4

Repeat testing in 4 PD patients with predictable motor fluctuations using the DFT and BRAIN test. Dots represent when the test was completed, and arrows denote the time when levodopa was taken. KS20 (DFT test) and KS30 (BRAIN test) scores are expected to increase in the ‘On’ state, whereas AT20 and AT30 scores are expected to decrease in the ‘On’ state.