Sample size estimates (per group) using change in slope of clinical scales.

Figures in cells are number of patients to be included per group, at α (2-tailed) = 0.05 and 1−β = 0.80, for different levels (30, 40, 50%) of expected change difference between groups on annual rate of change. Estimates for PSP, MSA or both groups combined, are based on effect sizes of NNIPPS-PPS, SEADL and UPDRS motor score (UPDRS-3) from the NNIPPS study, UMSARS [39] and PSP-RS [5]. Mean slopes ± SD as annual rate of change (points per year) are reported for each scale within each population.Abbreviations: PPS = Parkinson Plus scale; SEADL = Schwab & England Activities of Daily Living scale; UPDRS-3 = Unified Parkinson Disease Rating Scale (Motor examination score); PSP-RS = Progressive Supranuclear Palsy Rating Scale; UMSARS = Unified Multiple System Atrophy Rating Scale.