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

Abstract

Purpose: To translate the Trunk Impairment Scale (TIS), a measure of trunk control in patients with stroke, into Norwegian (TIS-NV), and to explore its construct validity, internal consistency, intertester and test-retest reliability. Method: The TIS was translated according to international guidelines. 201 patients with acute stroke were recruited for the validity study, and 50 inpatients with acquired brain lesions were recruited for the study of intertester and test-retest reliability. Construct validity was analysed using explorative factor analysis, 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 from the test. Six testlets were hierarchically constructed by combining items from the subscales Dynamic sitting balance and Coordination, and renamed modified TIS-NV (TIS-modNV). After these modifications the TIS-modNV fitted well to a locally dependent unidimensional item response theory model. The test demonstrated good construct validity, excellent internal consistency, as well as high intertester and test-retest reliability for the total score. Conclusions: The TIS-modNV is a valid and reliable scale for use in clinical practice and research.