Comparison of the responsiveness of the Barthel Index and the motor component of the Functional Independence Measure in stroke: the impact of using different methods for measuring responsiveness.

Two disability measures frequently used to assess the effects of interventions on stroke recovery are the Barthel Index (BI) and the motor component of the Functional Independence Measure (FIM Instrument). This study compared multiple measures of responsiveness of these instruments to stroke recovery between 1 and 3 months. Data on a 1- to 3-month change in the Instruments were obtained for 372 subjects who improved or maintained function on the modified Rankin Scale (MRS), using a subset of 459 eligible patients with confirmed stroke as defined by WHO criteria recruited from 12 participating hospitals in the Greater Kansas City area. Subjects were excluded because of death, early withdrawal from the study, missing MRS, or outcome data (57) decline on MRS (26), or inability to improve on MRS (4). Techniques used to assess responsiveness were: area under the ROC curve, Guyatt's effect size, paired t-statistics, standardized response mean, Kazis effect size, and mixed model adjusted t-statistic. The FIM Instrument and BI show little difference in responsiveness to change. The different responsiveness measures are generally consistent with this conclusion, with no measure clearly superior to the others. Large differences in the responsiveness measures were obtained within an instrument depending on the populations used (changers only or both changers and those who maintained function). Results also suggest responsiveness assessments are likely to be affected by time frame and phase of rehabilitation over which the responsiveness of a measure is determined.