Validation of a European Spanish-version of the Self-Evaluation of Negative Symptoms (SNS) in patients with schizophrenia.

ABSTRACT

INTRODUCTION: Negative symptoms can be grouped into five domains apathy/avolition, anhedonia, asociality, alogia, and affective flattening. There are few validate self-rated measures that assess these five dimensions. Therefore, this study aimed to validate the Self-Evaluation of Negative Symptoms (SNS) in Spanish patients with schizophrenia. MATERIAL AND METHODS: Cross-sectional, validation study in 104 outpatients with schizophrenia evaluated using the Spanish version of the following scales Clinical Assessment Interview for Negative Symptoms (CAINS), Positive and Negative Syndrome Scale (PANSS), Clinical Global Impression Scale for Schizophrenia (CGI-SCH), Personal and Social Performance (PSP), Motivation and Pleasure Scale - Self-Report (MAP-SR), 36-item Short-Form Health Survey (SF-36) and the Self-Evaluation of Negative Symptoms (SNS). RESULTS RELIABILITY Internal consistency (Cronbach's alpha) was 0.915. Convergent validity The Pearson correlation coefficient between MAP-SR and SNS Total scores was 0.660 (p<0.001). For PANSS-N, the correlation was 0.437 (p<0.005) and with the CAINS-Total was 0.478 (p<0.005). Divergent validity The Pearson correlation coefficient between SNS and PSP was r=-0.372 (p≤0.001), and with SF-36 Physical and Mental Summary Component scores were r=-0.213 (p=0.066) and r=-0.144 (p=0.219), respectively. Discriminant validity SNS Total scores were significantly statistically different according to the severity of the negative symptomatology rated by the CGI-SCH negative scale (p<0.001). CONCLUSION: The SNS is a reliable and valid instrument to self-rate the five domains of negative symptoms in patients with schizophrenia and seems to be appropriate for use in everyday clinical practice as a complementary measure to the evaluation performed by the clinician.