Question: How is an anxiety disorder diagnosed in seniors?
Answer: It's usually diagnosed with interview. The clinician will ask the client questions about the nature of the symptoms that they're having and determine whether those are consistent with the diagnosis of an anxiety disorder.
Sometimes that's supplemented with questionnaires or paper and pencil tests. And can also be further supplemented with a direct observations of the person in situations to see if their behavior is consistent with what you'd expect of an anxiety disordered individual.