Rate of change in early Huntington's disease: a clinicometric analysis.

Sensitive outcome measures for patients with Huntington's disease (HD) are required for future clinical trials. Longitudinal data were collected from a 3-year study of 379 patients suffering from early HD who were not treated by antipsychotics. Progression of UHDRS item scores was evaluated by linear regression and slope, whereas correlation coefficient, standard error, and P values were estimated on the basis of the data of eight evaluations from screening to study end (36 months). For the functional assessment dimension, the proportion of "no" responses at baseline and at study end was determined. Linear progression was observed for the motor score and for all three functional measures (i.e., functional assessment score, independence assessment score, and total functional capacity score). In contrast, there was little evidence for progression of the behavioral assessment score over the study period, whereas the cognitive assessment score was intermediate. Twenty-two motor-score items showed linear progression, with a slope of >0.003. These included all chorea items, finger tapping and pronation/supination (left and right), gait, tongue protrusion, and tandem walking. Different symptom domains and individual items evolved at different rates in this group of patients suffering from early HD. It may be possible to select sensitive items to create a simplified version of the UHDRS, which would be more efficient and more sensitive for the assessment of disease progression in clinical trials and natural history studies.