Self-assessment negative symptoms scale validation in Lithuania

Abstract

Introduction: Schizophrenia is a major health-care problem, but despite the importance of this issue, there were no validated tools for negative symptoms evaluation in Lithuania. Dolfus et al created a self-rated negative symptom scale (SNS) in concordance with the NIMH-MATRICS consensus statement on negative symptoms showing great psychometric properties. Therefore, we decided to validate this scale in Lithuania. Objectives: To validate the SNS in Lithuania and to evaluate the severity of negative symptoms of patients diagnosed with schizophrenia in Kaunas Clinics. Methods: We performed a double translation of SNS from French to Lithuanian then distributed the SNS, brief psychiatric rating scale (BPRS), mini international neuropsychiatric interview (MINI) to stable, non-psychotic patients diagnosed with schizophrenia according to ICD 10 in in-patient and out-patient settings. We measured internal consistency, convergent validity and discriminant validity comparing the results from SNS scale with negative and positive symptom scores from BPRS. We also performed principal component analysis, the factor retained had an eigenvalue >0,8. Results: We evaluated 51 patients. Cronbach’s coefficient (α = 0,8) showed good internal consistency. Factor analysis extracted one factor that accounted for 55,3 % of the variance. SNS score significantly correlated with negative subscores of BPRS (r = 0,87, p <0,001) and did not correlate with positive symptom subscores showing good convergent and discriminant validity. Mean score of SNS was 19,3 (SD = 9,2) with 54,8 % of patients scoring more than 20. Conclusions: SNS is a valuable tool for negative symptoms evaluation showing great psychometric properties. Most of the evaluated patients had severe negative symptoms.