SYMPTOM PROFILES OF PSYCHIATRIC-DISORDERS BASED ON GRADED DISEASE CLASSES - AN ILLUSTRATION USING DATA FROM THE WHO INTERNATIONAL PILOT-STUDY OF SCHIZOPHRENIA

The Grade of Membership (GoM) model is a classification procedure whic h allows a person to be a member of more than one diagnostic class. It simultaneously quantifies the degrees of membership in classes while generating the discrete symptom profiles or 'pure types' describing cl asses. The model was applied to the symptomatology, history, and follo w-up of 1065 cases in the WHO International Pilot Study of Schizophren ia. The model produced an eight diagnostic class or 'pure type' soluti on, of which five were related to the diagnostic concepts of schizophr enia and paranoid disorder, two types were affective disorders, and on e asymptomatic type. A subtype of paranoid schizophreniform disorder f ound primarily in developing countries was identified. There was a str ong association between pure types and the original clinical and compu ter generated (CATEGO) diagnoses. A GoM based psychiatric classificati on might more clearly identify core disease processes than conventiona l classification models by filtering the confounding effects of indivi dual heterogeneity from pure type definitions.