Abstract

Objective: Determine the extent to which estimates of sample and effect size in stroke rehabilitation trials can be affected by simple summation of ordinal Upper Extremity Fugl-Meyer (UEFM) items compared to a Rasch-rescaled UEFM. Design: Rasch analysis of ICARE Phase III trial data, comparing three upper extremity (UE) motor treatments in stroke survivors enrolled 45.8±22.4 days post-stroke. Participants underwent a structured UE motor training called Accelerated Skill Acquisition Program, usual and customary care, or dose-equivalent care. UEFM data from Baseline, post-intervention, 6, and 12 months were included for analysis. Setting: Outpatient stroke rehabilitation. Participants: ICARE participants. Interventions: N/A Main Outcome Measures: Item difficulties, person abilities, sample size. Results: Summed raw UEFM scores, because of their ordinality, measured motor impairment inconsistently across different ranges of stroke severity relative to the rescaled UEFM. In the full ICARE sample (N=361), raw UEFM understated scores relative to rescaled by 7.4 points for the most severely impaired, but overstated scores by up to 8.4 points towards the ceiling. As a result, 50.9% of all UEFM observations showed a residual error greater than 10% of the total UEFM score. Relative to the raw, the rescaled UEFM improved effect size of change in motor impairment between baseline and 1-year (d=0.35). For a hypothetical three-arm trial resembling ICARE, UEFM rescaling reduced required sample size by 32% (n = 108) compared to raw UEFM (n= 159). Conclusions: In UE rehabilitation trials, a rescaled UEFM potentially decreases sample size by 1/3, decreasing costs, duration, and subjects exposed to experimental risks. This benefit is obtained through increased measurement efficiency; reductions in ceiling effects are also possible. These findings apply to ICARE-like trials; confirmatory validation in another Phase III trial is needed.