Prodromal symptoms of schizophrenia in first-episode psychosis: prevalence and specificity.

Three hundred thirteen patients with first-episode psychosis were assessed using the Royal Park Multidiagnostic Instrument for Psychosis (RPMIP) to determine differences among seven DSM-III-R diagnoses in the comparative frequencies and diagnostic efficiencies of DSM-III-R schizophrenia prodromal symptoms. Patients with a diagnosis of schizophrenia and schizophreniform disorder were significantly more likely to evince prodromal symptoms. A multinomial logit model suggested that individual prodromal symptoms were relatively poor at distinguishing between diagnoses. This was confirmed when sensitivity, specificity, and positive (PPP) and negative (NPP) predictive power of individual prodromal symptoms were examined. Although DSM-III-R schizophrenia prodromal symptoms do occur more commonly in schizophrenia, they are by no means pathognomonic of that disorder.