In schizophrenia research, early detection in the initial prodrome before first psychotic episodes is a major topic. Therefore, the prognostic accuracy of initial prodromal symptoms was examined prospectively.
The study sample was composed of patients referred to outpatient departments of German psychiatric university departments, because of diagnostic problems, between 1987 and 1991. They were examined with the Bonn Scale for the Assessment of Basic Symptoms and the Ninth Version of the Present State Examination to detect an incipient schizophrenic disorder. Of 385 patients showing no schizophrenia-characteristic symptoms, between 1995 and 1998, 110 with and 50 without initial prodromal symptoms were followed up and reexamined with the same instruments for a transition to schizophrenia.
During a mean follow-up period of 9.6 years, 79 (49.4%) of the 160 patients had transited to schizophrenia. The absence of prodromal symptoms excluded a subsequent schizophrenia with a probability of 96% (sensitivity: 0.98; false-negative predictions: 1.3%), whereas their presence predicted schizophrenia with a probability of 70% (specificity: 0.59; false-positive predictions: 20%). Certain disturbances, such as thought interference, disturbances of receptive language, or visual distortions, predicted schizophrenia, even with a probability up to 91% (specificity: 0.85-0.91; false-positive predictions: 1.9%-7.5%).
The Bonn Scale for the Assessment of Basic Symptoms operationalization of prodromal symptoms performed well in the early detection of schizophrenia. It therefore might be useful for the prediction of the disorder, especially if it is further refined to select those items with particularly high prognostic accuracy.