Evaluation of the German translation of the Stroke Impact Scale using Rasch analysis.

To assess the complex and heterogeneous consequences of stroke, currently comprehensive patient-centered measures, like the Stroke Impact Scale (SIS), are increasingly being developed. The purpose of this study was to evaluate the psychometric properties of the German translation of the SIS using Rasch analyses. A total of 196 patients with stroke from 16 study centers participated in the study. In tests for item fit, 7 of the 64 items displayed model misfit. Response categories of 25 items showed threshold disordering. Person separation reliability lay above.80 in six domains. No differential item functioning was detected with respect to age, gender, disability severity, and setting. The results provide support for validity and reliability of the SIS, and also point out issues for further improvement and adaptation of the SIS.