Are positive and negative symptoms relevant to cross-sectional diagnosis of schizophrenic and schizoaffective patients?

The value of positive and negative symptoms for cross-sectional differential diagnosis was studied in a sample of 103 consecutively admitted patients with schizophrenia and schizoaffective psychoses. A semistructured interview for schizophrenia was used. Subjects were diagnosed by Research Diagnostic Criteria (RDC) and classified as schizophrenic, depressive schizoaffective, and manic schizoaffective disorders. DSM-III-R criteria for schizophrenia were used to assign RDC schizophrenics to two groups: "true" schizophrenic (fulfilling both DSM-III-R and RDC criteria) and schizophreniform (fulfilling RDC but not DSM-III-R criteria). The Scale for the Assessment of Positive Symptoms (SAPS) and Scale for the Assessment of Negative Symptoms (SANS) were used. Our findings showed that both positive and negative symptoms were relevant to differential diagnosis between schizophrenia and other psychotic disorders. However, negative symptoms presented higher significant differences between diagnostic groups than positive symptoms. These results were obtained by global ratings and by scoring on individual symptoms of SAPS and SANS. Treatment with neuroleptic and biperidene drugs did not alter symptomatologic differences between groups that resulted from repeated analyses of covariance. Certain symptoms and clusters of symptoms were found to be of higher severity of higher severity in only one diagnostic group. They were as follows: pressure of speech for manic schizoaffective disorder; guilt for depressive schizoaffective; high scores on negative symptoms for depressive schizoaffective and schizophrenic disorders; inappropriate affect for schizophrenic disorder; and three "psychomotor retardation" symptoms of the affective flattening subscale of SANS (unchanging facial expression, decreased spontaneous movements, and paucity of expressive gestures) for depressive schizoaffective disorder.(ABSTRACT TRUNCATED AT 250 WORDS)