Measurement Properties of the Nordic Questionnaire for Psychological and Social Factors at Work: A Rasch Analysis

The main aim of this study was to evaluate the measurement properties of the Nordic Questionnaire for Psychological and Social Factors at Work (QPS Nordic) and the domains of demand, control and support. The Rasch analysis (RUMM 2030) was based on responses from 226 subjects with back pain who completed the QPS Nordic dimensions of demand, control, and social support (30 items) at one year follow up. The Rasch analysis revealed disordered thresholds in a total of 25 of the 30 items. The domains of demand, control and support fit the Rasch model when analyzed separately. The demand domain was well targeted, whereas patients with current neck and back pain had lower control and higher support than reflected by the questions. Two items revealed DIF by gender, otherwise invariance to age, gender, occupation and sick-leave was documented. The demand, control support domains of QPS Nordic comprised unidimensional constructs with adequate measurement properties.