Background: The Overall Anxiety Severity and Impairment Scale (OASIS) is a 5-item self-report measure that can be used to assess severity and impairment associated with any anxiety disorder or multiple anxiety disorders. A prior investigation with a nonclinical sample supported the reliability and validity of the OASIS; however, to date it has not been validated for use in clinical samples.
Methods: The present study assessed the psychometric properties of the OASIS in a large sample (N=1036) of primary care patients whose physicians referred them to an anxiety disorders treatment study. Latent structure, internal consistency, convergent/discriminant validity, and cut-score analyses were conducted.
Results: Exploratory and confirmatory factor analyses supported a unidimensional structure. The five OASIS items displayed strong loadings on the single factor and had a high degree of internal consistency. OASIS scores demonstrated robust correlations with global and disorder-specific measures of anxiety, and weak correlations with measures of unrelated constructs. A cut-score of 8 correctly classified 87% of this sample as having an anxiety diagnosis or not.
Limitations: Convergent validity measures consisted solely of other self-report measures of anxiety. Future studies should evaluate the convergence of OASIS scores with clinician-rated and behavioral measures of anxiety severity.
Conclusions: Overall, this investigation suggests that the OASIS is a valid instrument for measurement of anxiety severity and impairment in clinical samples. Its brevity and applicability to a wide range of anxiety disorders enhance its utility as a screening and assessment tool.