Inaccurate Use of the Upper Extremity Fugl-Meyer Negatively Affects Upper Extremity Rehabilitation Trial Design: Findings From the ICARE Randomized Controlled Trial.

OBJECTIVE

To 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 with a Rasch-rescaled UEFM.

DESIGN

Rasch analysis of Interdisciplinary Comprehensive Arm Rehabilitation Evaluation (ICARE) phase III trial data, comparing 3 upper extremity (UE) motor treatments in stroke survivors enrolled 45.8±22.4 days poststroke. Participants underwent a structured UE motor training known as the Accelerated Skill Acquisition Program, usual and customary care, or dose-equivalent care. UEFM data from baseline, postintervention, and 6 and 12 months later were included for analysis.

SETTING

Outpatient stroke rehabilitation.

PARTICIPANTS

ICARE participants (N=361).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Item difficulties, person abilities, and sample size.

RESULTS

Because of their ordinality, summed raw UEFM scores measured motor impairment inconsistently across different ranges of stroke severity relative to the rescaled UEFM. In the full ICARE sample, raw UEFM understated scores relative to the rescaled UEFM by 7.4 points for the most severely impaired, but overstated scores by up to 8.4 points toward 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 scores, the rescaled UEFM improved the effect size of change in motor impairment between baseline and 1 year (d=0.35). For a hypothetical 3-arm trial resembling ICARE, UEFM rescaling reduced the required sample size by 32% (n=108) compared with raw UEFM (n=159).

CONCLUSIONS

In UE rehabilitation trials, a rescaled UEFM potentially decreases sample size by one-third, decreasing costs, duration, and the number of 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.