Assessing axis II disorders by informant interview.

Abstract

Although much of personality disorder research depends on diagnostic data obtained directly from patients, this approach has rarely been compared to interviews with knowledgeable informants. The purpose of this study was to determine the diagnostic agreement between these two assessment methods, as well as their relative contribution to the formulation of consensus diagnoses. Sixty-two psychiatric patients were assessed directly with the Structured Interview for DSM-III Personality Disorders (SIDP), and were asked to nominate an informant--either a family member or friend--to provide information about the patient in an interview with the same instrument. Informant interviews were conducted blind to patient-based information whenever feasible, and diagnostic consensus was achieved by an independent review of all available data by a senior clinician. Diagnostic agreement between patient-based and informant-based personality disorder interview was poor, confirming the findings of two previous studies. Information obtained from patients tended to be given greater weight in formulating consensus diagnoses than information provided by informants. However, about one quarter of diagnostic disagreements were resolved in favor of informant-based information. In contrast to a previous study, the inclusion of informant information did not appear to reveal greater psychopathology in patients. We conclude that supplementing direct patient interview with data provided by a knowledgeable informant appears to enhance the resolution of some personality disorder diagnoses. The utility of informant interviews may depend on an analysis of the costs and benefits of this additional degree of descriptive refinement.