Research in schizophrenia: necessity to include patients of multiple diagnostic systems]

The discrepancies of studies on symptomatology and treatment of schizophrenia could be related to the selection of different patients diagnosed by one diagnostic system, different from a study to another. Therefore, we tested whether 14 diagnostic systems could include 51 patients differently as regard to the intensity of positive, negative or depressive symptomatology and to the phase of illness. The distribution of the patients in different sets of diagnosis has been carried out by a computer program and the symptomatology has been evaluated with PANSS and MADRS. Some diagnostic criteria like DSMIII-R, Langfeldt, Taylor, ICD 9 include negative and depressive patients preferentially. Others systems like Berner, Catego, ICD 9, New-Haven, Schneider, include more patients with acute than residual symptoms. These results show the importance of the choice of one or more diagnostic criteria depending on the aim of the study.