Psychometric properties of the Overall Anxiety Severity and Impairment Scale (OASIS) among psychiatric outpatients

Background: The Overall Anxiety Severity and Impairment Scale (OASIS) is a brief, transdiagnostic measure used to assess anxiety severity and related interference. The OASIS has demonstrated strong psychometric properties in previous investigations, however, it has yet to be validated using a trans diagnostic clinician-rated measure. Methods: We evaluated the factor structure, convergent and discriminant validity, and illness severity cut-scores of the OASIS in a sample of outpatients (N=202). Results: A confirmatory factor analysis indicated an unidimensional structure provided the best fit. The OASIS demonstrated good convergent validity and internal consistency. Using the Clinical Global Impression-Severity Scale (CGI-S), ROC curves showed OASIS scores of 6, 10 and 12 to indicate moderate, marked and severe illness severity, respectively. Conclusions: The OASIS is a unidimensional self-report measure with good convergent validity and data from the current study provide illness severity cut-scores. (C) 2016 Elsevier B.V. All rights reserved.