Reliability and diagnostic validity for schizophrenia of the Japanese version of the Bonn Scale for Assessment of Basic Symptoms (BSABS).

Schizophrenia is defined by operative diagnostic criteria in DSM-IV with some typical symptoms as hallucinations and duration of the disease. Huber focused on the subjective experience of patients and coined the term "basic symptoms" and created BSABS. Our study investigated the reliability and the diagnostic validity of the 5 clusters of BSABS for DSM-IV-based diagnosis of schizophrenia with a cohort of 105 patients. Good inter-rater reliability was obtained except for one item D.10. As evaluated by Spearman's rank correlation coefficients, among the 5 clusters excluding Cluster 2, internal consistency was good. This suggests that, although each cluster is heterogeneous, cluster symptoms are the expression of physiological and biological disturbances of schizophrenia. Receiver Operating Characteristic Curve analysis was also used to show the ability of each cluster to discriminate schizophrenia. Results showed that the area representing the powers in discriminate schizophrenia of Cluster 4 "Adynamia", which is considered related to the dynamic aspect of thinking, was highest, at 0.739. Cluster 1 "Information processing disturbances" which has a predictive ability for schizophrenia showed 0.714 and Cluster 3 "Impaired tolerance to normal stress" showed 0.711. Our findings suggest that, although these clusters symptoms differ from DSM-IV criteria, they are related to fundamental process of schizophrenia. Use of some of these three clusters with other neurophysiological markers could allow clinical evaluation of schizophrenia from a new perspective.