Several studies suggest that a prototype-matching approach yields diagnoses of comparable validity to the more complex diagnostic algorithms outlined in the Diagnostic and Statistical Manual of Mental Disorders (4th ed.). Furthermore, clinicians prefer prototype diagnosis of personality disorders to the current categorical diagnostic system or alternative dimensional methods. An important extension of this work was to investigate the degree to which clinicians are able to make prototype diagnoses reliably. The aim of this study was to assess the interrater reliability of a prototype-matching approach to personality diagnosis in clinical practice. Using prototypes derived empirically in prior research, outpatient clinicians diagnosed patients' personality after an initial evaluation period. External evaluators independently diagnosed the same patients after watching videotapes of the same clinical hours. Interrater reliability for prototype diagnosis was high, with a median r ϭ .72. Cross-correlations between disorders were low, with a median r ϭ .01. Clinicians and clinically trained independent observers can assess complex personality constellations with high reliability using a simple prototype-matching procedure, even with prototypes that are relatively unfamiliar to them. In light of its demonstrated reliability, efficiency, and versatility, prototype diagnosis appears to be a viable system for the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders and the 11th edition of the International Classification of Diseases, with exceptional utility for research and clinical practice
