Rasch analysis staging methodology to classify upper extremity movement impairment after stroke

Abstract

Objectives: To define Fugl-Meyer Assessment of the Upper Extremity (FMA-UE) cutoff scores that demarcate 1 level of upper extremity (UE) impairment from another, and describe motor behaviors for each category in terms of expected FMA-UE item performance.

Design: Analysis of existing FMA-UE data.

Setting: University research laboratory.

Participants: Persons (N=512) 0 to 145 days poststroke, 42 to 90 years of age.

Intervention: Not applicable.

Main outcome measures: An item response Rasch analysis staging method was used to calculate cutoff scores, which were defined as the Rasch-Andrich threshold values of 2 criterion FMA-UE items derived from an analysis of this sample. The analysis enabled conversion of cutoff scores, in logit units, to FMA-UE points assessed on 30 FMA-UE voluntary movement items (60 possible points).

Results: The boundary between severe and moderate impairment was defined as -1.59 ± .27 logits or 19 ± 2 points; and between moderate and mild impairment was defined as 2.44 ± .27 logits or 47 ± 2 points. A description of expected performance in each impairment level shows that patients with severe impairment exhibited some distal movements, and patients with mild impairment had difficulties with some proximal movements.

Conclusions: The cutoff scores, which link to a description of specific movements a patient can, can partially, and cannot perform, may enable formation of heterogeneous patient groups, advance efforts to identify specific movement therapy targets, and define treatment response in terms of specific movement that changed or did not change with therapy.

Keywords: FMA-UE; Fugl-Meyer Assessment of the Upper Extremity; IRT; Rehabilitation; Stroke; UE; Upper extremity; item response theory; upper extremity.