Heterogeneity of delusional syndromes: diagnostic criteria and course prognosis.

In addition to genetic findings and treatment response, the course prognosis is also meant to be a possible validating criterion for diagnosis and diagnostic systems. In our study we used the polydiagnostic approach (i.e. the simultaneous application of various criteria for diagnosing a given disorder to one and the same population) to test the ability of several diagnostic systems to create homogeneous groups regarding the course (episodic/chronic). We applied Schneider's FRS, ICD-9, DSM-III, Spitzer's RDC and the Vienna Research Criteria to 90 patients with the diagnosis of delusional syndrome (aside from any nosological classification), who underwent 6-9 years of follow-up. At the index examination, schizophrenia was most frequently diagnosed with Schneider's FRS, which apparently encompasses a very heterogeneous group of patients regarding psychopathology and course. Diagnostic systems which allowed the diagnosis of affective disorders despite the presence of mood-incongruent delusional symptomatology (DSM-III, RDC, Vienna Criteria) or offered the diagnosis of schizoaffective disorder (DSM-III, RDC) succeeded in separating subgroups with an episodic course on a statistically significant level. In ICD-9 this significance appeared only after exclusion of the schizoaffective cases from the group of schizophrenias. Our data thus uphold the old rule of thumb that affective symptomatology apparently has a very high prognostic value regarding the course of the illness and is in this respect superior to productive symptomatology (such as delusions and hallucinations), still taken to be pathognomonic for schizophrenia by some of the diagnostic criteria under study. This aspect warrants further investigation and should be taken into account in the development and improvement of diagnostic manuals (e.g. ICD-10, DSM-IV).