Clinical utility of the Negative Symptom Assessment-16 in individuals with schizophrenia

Abstract

This study examined the clinical utility of the Negative Symptom Assessment-16 (NSA-16) in schizophrenia. 274 individuals with schizophrenia were assessed on the NSA-16, Positive and Negative Syndrome Scale (PANSS), Clinical Assessment for Negative Symptoms (CAINS), Calgary Depression Scale for Schizophrenia (CDSS), Social and Occupational Functioning Assessment Scale (SOFAS) and the Simpson-Angus Extrapyramidal Side Effects Scale (SAS). Factor analyses were conducted and Cronbach's alpha was computed. Correlations were assessed using Spearman's correlation coefficient. The 5-factor model of the NSA-16 did not give good fit statistics from our sample. Exploratory factor analysis on a randomly selected split-half of the sample followed by confirmatory factor analysis on the remaining sample supported a 4-factor structure with 12 items. The factors were: Restricted speech, Poor quality of speech, Affective blunting and Amotivation. The NSA-16 with the 12 items was termed as the NSA-12. The NSA-12 showed good internal reliability. The NSA-12 total score and global negative symptom rating had strong correlations with CAINS total and PANSS negative factor scores, suggesting good convergent validity. Weak correlations of the NSA-12 total score and global negative symptom rating with PANSS positive, CDSS and SAS scores suggested good divergent validity. The NSA-12 total score and global negative symptom rating were strongly and inversely associated with SOFAS and positively associated with NSA-12 global level of functioning. In conclusion, the NSA-12 is useful to evaluate negative symptoms in clinical and research settings in individuals with schizophrenia. Our study results also support a 4-factor structure of the NSA-12 in outpatients with schizophrenia.