Positive and negative symptoms/syndromes in schizophrenia: reliability and validity of different diagnostic systems

The paper explores the reliability, concurrent validity and overlap of some positive/negative symptom rating scales and typological criteria in 100 schizophrenic patients. Rating scales include Andreasen's Scales for the Assessment of Positive and Negative Symptoms, Abrams and Taylor's Scale for Emotional Blunting, and Kay's Positive and Negative Syndrome Scale. Criteria for categorizing individual patients include Andreasen's and Kay's criteria for positive and negative types of schizophrenia as well as Carpenter's criteria for the deficit syndrome. The correlations among positive as well as among negative scales were high. The agreement among criteria tended to be lower. Both positive scales showed low internal consistency. Kay's negative scale had the greatest internal consistency, which suggests that it is measuring a homogeneous syndrome. All negative symptom scales and categorical syndromes identified a group of patients who were single and exhibited schizoid or schizotypal pre-morbid personality disorders, poor premorbid sexual/social adjustment, poor response to neuroleptics and poor prognosis.