Evaluating the construct validity of the Trunk Impairment Scale: a Rasch analysis of its subscales


Verheyden, G. and Kersten, P. (2008) Evaluating the construct validity of the Trunk Impairment Scale: a Rasch analysis of its subscales. In, Society for Research in Rehabilitation, Leeds, UK, 03 - 04 Jul 2007.

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Description/Abstract

Background:
The Trunk Impairment Scale (TIS) evaluates static, dynamic sitting balance and trunk
coordination in people after stroke. This study aimed to evaluate the construct validity of
the subscales of the TIS.

Method
A total of 162 participants (mean age 67, SD=11), in all stages after stroke, were included
in the study. Rasch analysis (Partial Credit Model) was used (RUMM2020 software).

Results
There were no disordered thresholds on any of the polytomous items. The static sitting
balance subscale (SSB) did not fit the Rasch model (Chi-square=15.68; p=0.0004). We
were unable to examine DIF due to a large number of extreme cases in the dataset. The
dynamic sitting balance subscale (DSB) fitted the Rasch model (Bonferroni adjusted pvalue=
0.005) after splitting item 2 by Barthel categories to adjust for uniform DIF (Chisquare=
42.65; p=0.0052). The coordination subscale (COO) fitted the Rasch model and
did not display uniform or non-uniform DIF (Chi-square=7.87; p=0.446). In DSB and COO
fewer than 5% of the independent t-tests performed on person estimated locations were
significant, further supporting unidimensionality of these subscales. Graphical exploration
of thresholds for DSB and COO confirmed a hierarchy of dependent items. Person and
items were well distributed across the continuum of balance impairment.

Discussion
We were unable to examine SSB in full and further work with patients with very severe
static sitting balance impairments is needed. Item 2 of DSB needs to be given detailed
attention before assessing people after stroke.

Conclusion
Construct validity of two subscales was confirmed using Rasch analysis. Further work is
needed to examine SSB.

Item Type: Conference or Workshop Item (Paper)
Related URLs:
Subjects: R Medicine > RZ Other systems of medicine
Divisions: University Structure - Pre August 2011 > School of Health Sciences
ePrint ID: 58848
Date Deposited: 19 Aug 2008
Last Modified: 27 Mar 2014 18:41
URI: http://eprints.soton.ac.uk/id/eprint/58848

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