Rasch Analysis of the Wrist and Hand Fugl-Meyer: Dimensionality and Item-Level Characteristics

Abstract

Background and purpose: Clinical administration of the wrist stability, wrist mobility, and hand items of the upper-extremity Fugl-Meyer (W/H UE FM) may provide a rigorous, easily administered, bedside measure of motor impairment in mildly impaired stroke survivors. The purpose of this study was to evaluate the item structure of the W/H UE FM to better understand its measurement properties using Rasch analysis.

Methods: This was a secondary analysis of W/H UE FM data arising from clinical trials of mildly impaired stroke survivors using latent parallel analysis, ordinal factor analysis, and partial credit model Rasch analyses.

Results: Latent parallel analysis and ordinal factor analysis indicated that all W/H UE FM items represent a single unidimensional construct, wrist and hand motor ability. Rasch analysis of data from 150 mildly impaired stroke survivors (94 men; mean age, 57.1 ± 11.4 years; mean time since stroke, 19.5 months) revealed that the W/H UE FM operated as a reliable, valid, and effective measure of wrist and hand motor ability. These data were compatible with Rasch model assumptions and are consistent with previous W/H UE FM research. Mass flexion and extension movements were the least difficult W/H UE FM items while the radial and hook grasp items were the most difficult.

Discussion and conclusion: The W/H UE FM is well suited to mildly impaired stroke survivors who exhibit the ability to perform mass flexion and mass extension movements. The full-scale UE FM may be preferable for stroke survivors with lower levels of ability.Video abstract available for additional insight from the authors (Supplemental Digital Content 1, http://links.lww.com/JNPT/A108).

Figure 1

Plot of actual versus randomly generated eigenvalues. Data indicates that W/H UE FM data contribute to a single-construct, wrist and hand motor ability.

Figure 2

Cross-plot comparison of person measures resulting from the Rasch analysis of model 2 (140 people; 12 items) and model 3 (140 people; 10 items). The strong linear relationship depicted in the figure indicates that the removal of Items 6 and 8 did not significantly affect measurement precision.

Figure 3

The Modified Wright Map depicts the Rasch measure value (in logits) for both persons (n=150) and items (n=12) on the vertical axis. Harder items/ more able persons appear at the top of the graph and easier items/ less able persons fall at the bottom. The horizontal axis reflects the outfit t values (μ = 0, σ = 0) for each person and item. Larger circles reflect multiple persons. For example the large circle at the bottom of the figure represents the 10 people, with zero scores, who were temporarily removed from the analysis.