Measurement properties of the Swedish self-administered version of the World Health Organization Disability Assessment Schedule 2.0

Sammanfattning: The World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) is a leading patient-reported outcome measure of disability. However, patients' perspective of the WHODAS 2.0 self-administered Swedish version have not been sufficiently described. Similarly, knowledge of its construct validity in the general population is missing. This creates a gap because updated norm data to use as reference is also missing. The overall aim of this study was to establish evidence of the measurement properties of the self-administered Swedish version of the WHODAS 2.0.Both qualitative and quantitative methods were adopted. In Study I, interviews with patients (n = 12) with orthopaedic or psychiatric conditions were performed and data were analysed by deductive content analysis. In Study II, a cross-sectional general population survey (n = 3 482) was conducted, and statistical methods based on classical test theory were used in the data analysis.The results show that the items were well understood, acceptable and easy to answer by outpatients, with the exception of six items (Study I).The internal consistency reliability was good or excellent and the construct validity was overall acceptable, with partial support for the factor structure in the general populations (Study II).The self-administered Swedish 36-item version of the WHODAS 2.0 is comparable to other language versions of the instrument. Some of the previous known weaknesses of its construct validity in relation to the item content and insufficient instructions were confirmed. The evidence of overall good content and construct validity together with available norm data supports its use in clinical settings and research.