Abstract
Objective
To develop and evaluate psychometrically a self-reported instrument assessing physical
fatigability (PF) and mental fatigability (MF) in adults with spinal cord injury (SCI).
Design
Cross-sectional.
Setting
Peer-support groups at rehabilitation centers, online support groups.
Participants
Adults with SCI (N=464) in the United States.
Interventions
Not applicable.
Main Outcome Measures
The dimensional structure was assessed by confirmatory factor analysis. The relationship
between item responses and fatigability was measured with item response theory (graded
response model). Reliability was measured with test information functions. Differential
item functioning was evaluated with Wald chi-square tests and the weighted area between
the curves. Construct validity was assessed using the known groups method.
Results
An 82-item pool was developed from prior qualitative research and consultations with
rehabilitation experts. A non-probability sample (N=464) was used to evaluate the
psychometric properties of the PF and MF scales. The item pool was reduced to 75 based
on factor loadings and R2. Both scales are primarily unidimensional, despite moderate multidimensionality.
There is good discrimination overall: 18 PF items and 26 MF items have high or very
high discrimination power (slopes > 1.35). The measurement precision in the theta
range -2.0 to 2.5 is the equivalent of 0.94 reliability for PF and 0.91 for MF. For
both measures, F statistics P values were significant at P<.01, and means were higher for those with paraplegia vs quadriplegia, and for those
with incomplete paraplegia.
Conclusions
The Fatigability Index is the first instrument designed to assess physical and mental
fatigability in adults with SCI. The index highlights causes of fatigue and areas
requiring immediate intervention. Development of short-forms and further research
on representative samples are necessary.
Keywords
List of abbreviations:
SCI (spinal cord injury), PF (physical fatigability), MF (mental fatigability), CFA (confirmatory factor analysis), IRT (item response theory), DIF (differential item functioning), wABC (weighted area between the curves), RMSEA (Root Mean Square Error of Approximation), CFI (Comparative Fit Index), TLI (Tucker-Lewis Index), PUC (percent uncontaminated correlations), ECVGEN (explained common variance on the general dimension), I-ECV (individual explained common variance)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: April 25, 2018
Footnotes
Supported by a University of California Los Angeles Dissertation Year Fellowship (Palimaru); the Resource Centers for Minority Aging Research/Center for Health Improvement of Minority Elderly (RCMAR/CHIME) under National Institutes of Health/National Institute on Aging (NIH/NIA) grant no. P30-AG021684 (Hays); and the RCMAR/CHIME under NIH/NIA grant no. P30-AG021684 and the NIH/National Institute for Minority Health and Health Disparities (NIMHD)/2P20MD000182-11/Excellence in Partnerships for Community Outreach, Research on Health Disparities and Training Center (Drew-UCLA Project EXPORT Center) (Cunningham). The funders had no role in the study design, data collection, analysis and interpretation of data, writing of the report, or decision to submit the article for publication.
Disclosures: none.
Identification
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© 2018 by the American Congress of Rehabilitation Medicine
