A Dutch version of the Overall Anxiety Severity and Impairment Scale (OASIS): Psychometric properties and validation.

Background: The Overall Anxiety Severity and Impairment Scale (OASIS) is a 5-item self-report measure that can be used to assess the impact of any anxiety disorder or multiple anxiety disorders. Prior US investigations have shown the OASIS to be a reliable and valid measure. To date the OASIS has not been validated for use in a Dutch sample of anxiety disordered patients.

Methods: The present study assessed the psychometric properties of a Dutch version of the OASIS in a clinical sample of anxiety patients. Latent structure, internal consistency, convergent and discriminant validity, and cutoff score analyses were conducted. Results were compared to those obtained from a clinical sample of patients with psychiatric diagnoses other than anxiety disorders.

Results: Principal component analysis supported a unidimensional structure. The five OASIS items loaded strongly on a single factor (eigenvalue=3.682, loadings=.80-.89) which accounted for 73.65% of the variance, and had a high degree of internal consistency (Cronbach׳s α=91). OASIS scores demonstrated robust correlations with other measures of anxiety, neuroticism and general distress. Correlations with unrelated constructs were weak. Mean score (8.46) and cutoff score of the Dutch sample of anxiety patients were lower than scores previously found in American samples. A cutoff score of 5 correctly classified 82.5% of this sample as having an anxiety disorder diagnosis or not. An improvement of 4 points is indicative of a clinically significant change.

Limitations: This study mainly relied on self-report measures in order to assess validity. Other types of measures should be used in future studies.

Conclusions: The Dutch version of the OASIS showed good reliability and validity. Its brevity and sound psychometric properties make it a good instrument for screening and assessment purposes in the field of anxiety disorders.