F038 Longitudinal relationship between the Huntington’s disease digital motor score and clinical scales

<h3>Background</h3> The Huntington’s Disease Digital Motor Score (HDDMS) promises to measure HD progression with higher sensitivity than standard clinical measures. To establish its longitudinal validity, the relationship between change in the HDDMS and standard clinical measures needs to be explored. However, comparatively short observation windows coupled with high variability of the assessments may confound the results. <h3>Aims</h3> Relate HDDMS change from baseline and change from baseline of cUHDRS and its components using different methods in order to increase the robustness of our conclusions. <h3>Methods/Techniques</h3> Using 16 months of data from GENERATION HD1, we explored the change-to-change relationship using correlations and principal component analysis (PCA). PCA can inform about the shared variance of features and was previously used to select the cUHDRS components (Schobel et al., 2017). <h3>Results/Outcome</h3> There are small but significant change-to-change correlations between cUHDRS and its components and the HDDMS (e.g. yearly change correlation coefficient between HDDMS and cUHDRS = -0.29, p-value = 0.0002). PCA confirms published results and indicates that the HDDMS both cross-sectionally and longitudinally captures similar signal as the cUHDRS components. In particular, the different measures contribute equally to the first principal component of both the baseline and the longitudinal PCA. <h3>Conclusions</h3> There is consistent evidence that the HDDMS is sensitive to similar aspects of disease progression as standard clinical measures of HD. As a consequence, due to the inherent variability of the assessments and the slow progression of HD, the ability of the HDDMS to predict change in cUHDRS over a 16 month timespan remains limited.