Psychometric evaluation of the Psychotic Symptom Rating Scales.

BACKGROUND: The aims of this study were to examine the psychometric properties of a German version of the Psychotic Symptom Rating Scales (PSYRATS) in a sample of patients with schizophrenic spectrum disorders and affective disorders with delusions and to validate subscales of the PSYRATS with other ratings of psychotic symptoms. SAMPLING AND METHODS: Two hundred patients with schizophrenic spectrum disorder and affective disorders with delusions were examined. Psychometric properties of the PSYRATS items and scales were determined, and the scores of the PSYRATS scales and subscales were compared to the Positive and Negative Syndrome Scale (PANSS) and other ratings of psychotic symptoms. RESULTS: The PSYRATS items and scales were found to have excellent interrater reliability. Two factors for the delusions scale (DS) and 4 factors of the auditory hallucinations scale were found. Subscales of the DS and auditory hallucinations scale were replicated by factor analysis, and the validity of the subscales was supported. CONCLUSIONS: The German version of the PSYRATS is a reliable and valid assessment tool for delusions and hallucinations. The findings support the validity of the PSYRATS subscales. The DS is also applicable for patients with affective disorders.

Psychometric evaluation of the characteristics of delusions rating scale as an expert rating scale.

BACKGROUND: Research suggests delusions may be better viewed as multidimensional rather than dichotomous phenomena. The aim of this study was to assess the reliability and validity of a German version of the Characteristics of Delusions Rating Scale (CDRS) as an expert rating scale. METHOD: 200 inpatients with schizophrenic spectrum and affective disorders with delusions were assessed with the CDRS and other delusion rating scales. Factorial validity was analysed, and differences between diagnostic groups on the CDRS subscales as well as on the total score were examined. RESULTS: The CDRS was found to have good inter-rater reliability and internal consistency as an expert rating. Factor analysis yielded an interpretable structure with 3 factors - cognition, emotion and bizarreness - accounting for 70% of the variance. The convergent and differential validity of the scales was supported. Compared to other scales, the CDRS measures all dimensions of delusional experience that have been suggested to date with the exception of behavioural aspects. CONCLUSIONS: The results support the view of delusions as multidimensional phenomena. The CDRS as an expert rating is a reliable and valid assessment tool for dimensions of delusional experience and an economical instrument for research and clinical practice. Further research is needed to examine the dimensional structure underlying delusional phenomena and the relationship of the dimensions to neurobiological and psychotherapeutic processes.