When used appropriately, IRT can be a powerful tool for questionnaire development, evaluation, and refinement, resulting in precise, valid, and relatively brief instruments that minimize response burden.

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Background This study prospectively examined the natural clinical course of six anxiety disorders over 7 years of follow-up in individuals with personality disorders (PDs) and/or major depressive disorder. Rates of remission, relapse, new episode onset and chronicity of anxiety disorders were examined for specific associations with PDs. Method Participants were 499 patients with anxiety disorders in the Collaborative Longitudinal Personality Disorders Study, who were assessed with structured interviews for psychiatric disorders at yearly intervals throughout 7 years of follow-up. These data were used to determine probabilities of changes in disorder status for social phobia (SP), generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), panic disorder and panic disorder with agoraphobia. Results Estimated remission rates for anxiety disorders in this study group ranged from 73% to 94%. For those patients who remitted from an anxiety disorder, relapse rates ranged from 34% to 67%. Rates for new episode onsets of anxiety disorders ranged from 3% to 17%. Specific PDs demonstrated associations with remission, relapse, new episode onsets and chronicity of anxiety disorders. Associations were identified between schizotypal PD with course of SP, PTSD and GAD; avoidant PD with course of SP and OCD; obsessive-compulsive PD with course of GAD, OCD, and agoraphobia; and borderline PD with course of OCD, GAD and panic with agoraphobia. Conclusions Findings suggest that specific PD diagnoses have negative prognostic significance for the course of anxiety disorders underscoring the importance of assessing and considering PD diagnoses in patients with anxiety disorders.