Methods: The 24-item clinician-rated Sydney Melancholia Prototype Index (SMPI-CR) was completed for
364 unipolar depressed patients. The sample was divided into two cohorts according to the recruitment
period. An RPART classification tree analysis identified the most discriminating SMPI items in the
development sample of 197 patients, and examined the sensitivity and specificity of the diagnostic
decisions, then sought to replicate findings in a validation sample of 169 patients.