Background Speeded (ST) and metronome (MT) tapping have been shown to be sensitive in distinguishing premanifest (preHD) and manifest (HD) stages of Huntington's disease (HD) in the cross-sectional analysis of the TRACK-HD study, and to detect an early motor phenotype even more than 14 years before predicted disease manifestation.

Aims To investigate whether ST and MT are able to track disease progression within a 12 month follow-up period.

Methods Participants from the four TRACK-HD sites (ST/MT: controls: 120/122, preHD: 117/118, HD: 117/121) were instructed to perform two tapping tasks with their non-dominant index finger. In ST, they had to tap at maximal speed for 10s; in MT, they were instructed to continue a given tapping rate of 1.8 Hz for 10s. After one year, the assessments were repeated. The annual change in performance of gene-carriers was compared to controls and to each other. The variability of tapping intervals expressed as logarithmic standard deviations was calculated for the primary outcome measures (ie, inter-onset interval (IOI) & tap duration (TD) in ST, inter-onset intervals (ΔIOI) & mid-tap interval (ΔMTI) in MT).

Results The annual change in IOI and TD for ST showed significant results for HD versus controls and HD versus preHD. ΔIOI and ΔMTI, both MT variables, failed to make this distinction.

Conclusions ST is able to detect changes in manifest HD within only one year of follow-up and may thus be applicable as an outcome measure for disease modifying clinical trials in early manifest HD. Possible changes in preHD may require longer follow-up periods or larger cohorts. The hypothesis that force-transducer-based MT and ST tasks may track the progression of a premanifest motor phenotype will be tested in the TRACK-HD study.