Psychometric testing of the Icelandic Occupational Self-Assessment (OSA-IS)

The Occupational Self-Assessment (OSA) is a self-report measure of occupational competence and values used to identify goals and assess outcomes. The Icelandic version of the OSA (OSA-IS) has been through several developmental stages to evaluate its psychometric properties. Through each stage, revisions have been made. To investigate the psychometric properties of the fourth revised version of OSA-IS. Retrospective data from 291 rehabilitation clients with a range of conditions were analysed using Rasch analysis of unidimensionality and descriptive statistics. All statistics were compared to established criteria. Analyses suggest the OSA-IS items define unidimensional constructs of occupational competence and values. Most (89%) participants completed the assessment in a reliable manner and no association was observed between demographic variables and fit status. Differences in the item hierarchies were observed between the original OSA and the OSA-IS, suggesting that Icelandic clients responded differently due to cultural, linguistic and/or sample differences. OSA-IS is a psychometrically sound instrument that may be used to support identification of client-centred goals and for intervention development. Clinicians should use score tables specifically developed for the OSA-IS to measure outcomes.