The Trunk Impairment Scale - modified to ordinal scales in the Norwegian version.

PURPOSE To translate the Trunk Impairment Scale (TIS), a measure of trunk control in patients after stroke, into Norwegian (TIS-NV), and to explore its construct validity, internal consistency, intertester and test-retest reliability. METHOD TIS was translated according to international guidelines. The validity study was performed on data from 201 patients with acute stroke. Fifty patients with stroke and acquired brain injury were recruited to examine intertester and test-retest reliability. Construct validity was analyzed with exploratory and confirmatory factor analysis and item response theory, internal consistency with Cronbach's alpha test, and intertester and test-retest reliability with kappa and intraclass correlation coefficient tests. RESULTS The back-translated version of TIS-NV was validated by the original developer. The subscale Static sitting balance was removed. By combining items from the subscales Dynamic sitting balance and Coordination, six ordinal superitems (testlets) were constructed. The TIS-NV was renamed the modified TIS-NV (TIS-modNV). After modifications the TIS-modNV fitted well to a locally dependent unidimensional item response theory model. It demonstrated good construct validity, excellent internal consistency, and high intertester and test-retest reliability for the total score. CONCLUSIONS This study supports that the TIS-modNV is a valid and reliable scale for use in clinical practice and research.