Introduction and objectives: The temporal stability of the positive and negative symptoms in schizophrenia deserves a special interest due to its consequences in the outcome and the treatment of the disease. This study determines the temporal stability of positive/negative subtypes in schizophrenia during the acute phase.
Material and methods: This is a clinical, observational and prospective study of a dynamic cohort of patients with acute exacerbation of schizophrenia defined by DSM III-R criteria. Patients with severe and unstable organic pathology, substance dependence, mental organic disorder, mental retardation, depression, or medicamentous parkinsonism were excluded. Clinical assessment was performed with the PANSS scale. Schizophrenic subtypes were established according to inclusive and restrictive criteria of PANSS. All patients were treated with new antipsycotics and biperiden if necessary.
Results: 51 patients were assessed for 8 weeks. In the baseline, the negative subtype (63.3% and 52.5% by inclusive and restrictive system respectively) and paranoid form (45.1%) were predominant. Three types of analysis were performed to determine the temporal stability: 1. Concordance (Kappa index). The concordance of the inclusive and restrictive System, regarding to the baseline assessment, indicated that both criteria had a low temporal stability. 2. Mc Nemar Ji Square. This test showed that these changes were bi-directional except for the first visit, which was significant through the restrictive system (higher change from the negative to other subtypes). 3. Transition analysis among groups by First Order Morkov Chains analysis indicated that this change was stationary (the change was the same in all phases).
Conclusions: 1o The variable "time" has to be considered for the definition of subtypes in schizophrenia. 2o The restrictive system is more specific. It allows to identify a subgroup of patients with "Negative" schizophrenia with a high specificity and validity in clinical and epidemiological studies. 3o The use of the baseline visit as a reference (gold standard) is recommended because it exits a higher concordance among criteria and a more florid psychopathology.