Dimensionality and Item-Difficulty Hierarchy of the Lower Extremity Fugl-Meyer Assessment in Individuals with Subacute and Chronic Stroke Presented in part as a poster to the American Congress of Rehabilitation Medicine, November 13, 2013, Orlando, FL.
Abstract
Objective To investigate the dimensionality and item-difficulty hierarchy of the Fugl-Meyer Assessment of the lower extremity (FMA-LE). Design Secondary analyses of data pooled from 4 existing datasets: a phase III randomized controlled trial investigating the effectiveness of body weight support and a treadmill for rehabilitation of walking poststroke, and 3 cross-sectional studies investigating the link between impaired motor performance poststroke and walking. Setting University research centers and rehabilitation centers. Participants A pooled sample of individuals with a stroke (N=535, men=313; mean age ± SD, 61.91±12.42y). Interventions Not applicable. Main Outcome Measures Confirmatory factor analyses (CFA) and Rasch residual principal component analysis (PCA) investigated the dimensionality of the FMA-LE. The Rasch analysis rating scale model investigated item-difficulty hierarchy of the FMA-LE. Results The CFA showed adequate fit of a 3-factor model, with 2 out of 3 indices (CFA=.95; Tucker-Lewis Index=.94; root mean square error of approximation=.124) showing good model fit. Rasch PCA showed that removal of the reflex and coordination items explained 90.8% of variance in the data, suggesting that the abnormal synergy items contributed to the measurement of a unidimensional construct. However, rating scale model results revealed deviations in the item-difficulty hierarchy of the unidimensional abnormal synergy items from the originally proposed stepwise sequence of motor recovery. Conclusions Our findings suggest that the FMA-LE might represent a multidimensional construct, challenging the use of a total score of the FMA-LE to predict lower extremity motor recovery. Removal of the misfit items resulted in creation of a unidimensional scale composed of the abnormal synergy items. However, this unidimensional scale deviates from the originally proposed hierarchical ordering.