Abstract
Objective
To perform a comprehensive analysis of the psychometric properties and dimensionality
of the Upper Limb Functional Index (ULFI) using both classical test theory and Rasch
analysis (RA).
Design
Prospective, single-group observational design.
Setting
Freestanding rehabilitation center.
Participants
Convenience sample of Italian-speaking subjects with upper limb musculoskeletal disorders
(N=174).
Interventions
Not applicable.
Main Outcome Measures
The Italian version of the ULFI. Data were analyzed using parallel analysis, exploratory
factor analysis, and RA for evaluating dimensionality, functioning of rating scale
categories, item fit, hierarchy of item difficulties, and reliability indices.
Results
Parallel analysis revealed 2 factors explaining 32.5% and 10.7% of the response variance.
RA confirmed the failure of the unidimensionality assumption, and 6 items out of the
25 misfitted the Rasch model. When the analysis was rerun excluding the misfitting
items, the scale showed acceptable fit values, loading meaningfully to a single factor.
Item separation reliability and person separation reliability were .98 and .89, respectively.
Cronbach alpha was .92.
Conclusions
RA revealed weakness of the scale concerning dimensionality and internal construct
validity. However, a set of 19 ULFI items defined through the statistical process
demonstrated a unidimensional structure, good psychometric properties, and clinical
meaningfulness. These findings represent a useful starting point for further analyses
of the tool (based on modern psychometric approaches and confirmatory factor analysis)
in larger samples, including different patient populations and nationalities.
Keywords
List of abbreviations:
CTT (classical test theory), DASH (Disability of the Arm, Shoulder, and Hand), MnSq (mean square), PCA (principal component analysis), RA (Rasch analysis), ULFI (Upper Limb Functional Index)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: September 17, 2014
Footnotes
Disclosures: none.
Identification
Copyright
© 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
