Can clinical features of bipolar-I disorder be assessed reliably on the telephone?

Background: The reliability of telephone interviews for rating 25 selected individual items of the Diagnostic Interview for Genetic Studies (DIGS) was assessed among persons with remitted bipolar disorder I (BPD I, n=20). Methods: The Diagnostic Interview for Genetic Studies (DIGS) was administered directly (with two raters present) and by telephone in random order to 20 adults with bipolar disorder I. Results: Telephone interviews achieved reliability comparable to direct interviews for 16 items (64%), but were considered unsatisfactory for seven others (28%). Two other items, which evaluated the overlap between substance abuse and mood disorder, were considered unreliable for both methods of interview. Limitations: The presence of two interviewers for the in-person interview may have led to over-estimation of in-person reliability. Investigator bias in favor of phone interviews and a relatively small sample may have confounded the results. Conclusions: Telephone interviews may be used to evaluate individuals with BPD I in remission, provided the limitations of this method are recognized. They have limited reliability for dissecting overlap between mood abnormalities and psychotic phenomena or substance abuse.