A comparison of instrument sensitivity to negative symptom change

Accurate assessment of negative symptom changes in schizophrenic patients is crucial to determining the efficacy of new treatments. The present study examined the sensitivity to change over the course of hospitalization in negative symptomatology assessed by the Scale for the Assessment of Negative Symptoms (SANS), the Negative Symptom Assessment (NSA), and an expanded version of the Brief Psychiatric Rating Scale (BPRS) in a sample of 60 schizophrenic patients. Symptoms were assessed when the patients were acutely ill and again when they were stabilized. Effect sizes were compared across all three rating scales. The retardation factor of the BPRS had a relatively small effect size (0.32). Effect size for the total NSA was 0.78 and ranged from 0.38 to 0.87 for the SANS. Individual factors had moderate to large effect sizes that ranged from 0.18 to 0.91 for both scales. Separate analyses were performed to calculate effect sizes for a five-factor version of the NSA and to examine only those symptoms specified in DSM-IV (alogia, affective flattening, and avolition). Effect sizes relatively comparable to those found for the entire SANS and NSA scales were found for the separate calculations. Results indicate that the addition of a negative symptom assessment instrument to research protocols increases the ability to detect changes in negative symptoms with substantially fewer subjects than would be required with the BPRS retardation factor alone.