Objective: To validate a timed tapping task (TTT) on a smartphone to ascertain differences in OFF- and ON-phases in Parkinson’s disease (PD) in the home setting.

Background: Objective determination of ON-OFF periods is important for adequate medication dosing as well as for research purposes. The validity and feasibility of assessing ON-OFF fluctuations using a TTT on a smartphone has the potential to be used at home but was so far not studied before.

Method: During 7 days, 17 right-handed patients (age 66±10 and H&Y 2.0±0.4) performed the TTT every morning before the first medication intake at home. This was followed by two trials 1 and 3 hours after medication intake (ON₁; ON_3h). During 30s, patients moved their index finger as fast as possible between 2 targets presented on a smartphone. Reminders were set for testing and medication intake. After each trial a visual analogue scale (VAS), rating subjective ON-OFF status, was completed. Outcomes were tap frequency, inter-tap time, and inter-tap distance. To assess construct validity, correlation analysis between TTT outcomes and MDS-UPDRS-III upper limb scores (ON) was performed. For test-retest reliability ON_1h vs ON_3h was compared with the intraclass correlation coefficient (ICC) on day 2 and 7.

Results: Average performance over 7 days showed a decreased frequency (p<0.01) and increased inter-tap time (p<0.05) OFF compared to ON₁ and ON_3h. Results showed learning effects, with significantly improved performance, albeit equally in ON and OFF after day 2 (all p≤0.04). No significant ON-OFF differences were found for inter-tap distance. 14 patients were able to complete 3 tests on all 7 days without >40 min delay. Correlation analysis revealed associations, between MDS-UPDRS-III upper limb scores and frequency (r≥0.53, p≤0.03) and inter-tap time (r≥0.57, p≤0.02) in both ON and OFF, but not with subjective ON and OFF status. The TTT showed excellent test-retest reliability for frequency (ICC ≥0.80), inter-tap time (ICC ≥0.85) and distance (ICC ≥0.55) on both days.

Conclusion: The smartphone-based TTT is a feasible and sensitive task to detect OFF and ON states in PD with good construct validity and excellent test-retest reliability. This test can be a useful addition to e-diary developments and in clinical studies in which a precise estimation of medication state is indispensable.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/home-validation-of-a-smartphone-based-tapping-task-to-assess-medication-responsiveness-in-parkinsons-disease/