Measurement properties of the Swedish modified version of the Postural Assessment Scale for Stroke Patients (SwePASS) using Rasch analysis

Background A previous small-sample (N.=150) Rasch analysis of the Swedish modified version of the Postural Assessment Scale for Stroke Patients (SwePASS) suggested problems regarding response categories and redundant items that need confirmation in larger samples with more severe strokes. Aim The aim of this study was to evaluate the measurement properties of the SwePASS in patients with acute stroke. Design A multicenter, cross-sectional study. Setting Two stroke units in Western Sweden. Population The study cohort included 250 consecutive inpatients undergoing rehabilitation after acute stroke. Methods The SwePASS assessments were performed once within the first four days after admission to the stroke units. The data were analyzed according to the Rasch measurement model regarding targeting, model fit, reliability, response category function, local dependence and differential item functioning. Results Postural control of 250 patients (median age, 76.5 years) was assessed with the SwePASS within median of two days after admission to the stroke units. The SwePASS covered a continuum of different levels of postural control, but had suboptimal targeting with insufficient representation of lower and higher levels of postural control. The reliability was high, the item fit statistics were generally acceptable and there was no differential item functioning by sex, age and stroke localization. However, response categories did not function as expected for four of the 12 SwePASS items and five items exhibited local dependency. Conclusions The SwePASS exhibited several promising measurement properties. To improve the scale, poor targeting, illogical response categories and local dependency should be addressed. Clinical rehabilitation impact The SwePASS provides valuable clinical information regarding postural control in the acute phase after stroke.