The psychometric properties of the Self-Evaluation of Negative Symptoms Scale (SNS) in treatment-resistant schizophrenia (TRS)

Abstract

Background: Clinician-administered measures of negative symptoms may not capture patients' subjective experiences. The Self-Evaluation of Negative Symptoms (SNS) has shown good psychometric properties when used in outpatients with higher-level functioning schizophrenia. We aimed to evaluate the psychometric properties of the SNS in low functioning participants with treatment-resistant schizophrenia (TRS).

Methods: Participants were assessed using the following measures at two time-points; time-point 1: SNS, Wide Range Achievement Test, 4th Edition Reading Subtest (WRAT-4), and Brief Assessment of Cognition in Schizophrenia (BACS). Time-point 2 (within a week of time-point 1): SNS, Negative Symptom Assessment 16 items (NSA-16), Scale to Assess Unawareness in Mental Disorder-Abbreviated (SUMD-A), Clinical Global Impression Severity Scale (CGI-S), Simpson Angus Scale (SAS), Calgary Depression Scale for Schizophrenia (CDSS), and the Patient Feasibility Questionnaire.

Results: Fifty participants with TRS were enrolled, a mean age of 43.8 years (SD = 11.19, min = 25, max = 64), a mean IQ of 80.62 (SD = 17.12, min = 65, max = 110), and a mean BACS Composite T-Score of 14.08 (SD = 17.16, min = -27, max = 49). Participants responded to SNS prompts with moderate consistency across two time-points. There were no significant correlations between the SNS and the NSA-16 Global Symptom score (Pearson r = 0.207, p = .150, Spearman r = 0.101, p = .483), NSA-16 Global Functioning score (Pearson r = 0.209, p = .145, Spearman r = 0.126, p = .384), nor the NSA-16 total score (Pearson r = 0.149, p = .302, Spearman r = 0.116, p = .421). However, when participants were stratified by BACS Composite T-score, there was a significant positive correlation between the SNS total and the NSA-16 Global Functioning score (Pearson r = 0.500, p = .048, Spearman r = 0.546, p = .029) among participants who demonstrated higher cognitive functioning.

Conclusion: Participants with TRS and low functioning were able to respond to questions on the SNS regarding their subjective assessment of negative symptoms. However, self-reported and clinician-rated negative symptoms were not equivalent, except in a subgroup with higher cognitive functioning. This discrepant self-reporting appeared to relate to their low levels of insight and cognitive impairments.

Keywords: Insight; Negative symptoms; Self-assessment; Treatment-resistant schizophrenia.