Brief rating instrument for assessment of negative symptoms: Derived from the Comprehensive Psychopathological Rating Scale (CPRS)

Abstract

Introduction: the aim of the study was to investigate whether a scale based on 10 selected items from the Comprehensive Psychopathological Rating Scale (CPRS) correlated with the widely used Schedule for the Assessment of Negative Symptoms (SANS) in measuring symptom severity and change in a group of patients suffering from chronic schizophrenia. Method: ninety patients with a diagnosis of schizophrenia were recruited from five British clinical services. The patients were all resistant to conventional antipsychotic medication. The patients were divided into two groups that received Befriending (BF) or Cognitive-behavioural therapy (CBT). The patients were scored on the CPRS and the SANS three times, before and after the therapy and again at 9 months follow-up. Tests for normality or skewness confirmed a normal distribution and therefore Pearson's correlation coefficient was used. Results: the initial assessment showed a correlation of 0.56, the second had a correlation of 0.57, whilst the last follow-up correlation had increased to 0.87. Conclusion: the correlations at all three assessment points were acceptable. The new rating scale is (a) shorter than the SANS; (b) a valid measure of negative symptom severity; (c) sensitive to change; and (d) allows negative symptom scores to be abstracted from CPRS ratings.