Validation de la version française de l’échelle autoévaluation des symptômes négatifs (SNS)

Abstract

IntroductionSchizophrenia is a disorder affecting 1% of the population and is associated with severe functional impairment. Negative symptoms are responsible for the majority of this impairment, and many patients with schizophrenia have negative symptoms. However, their evaluation is still a challenge. Thus, standardized assessments are needed to facilitate identification of these symptoms. Many tools have been developed, but most are based on observer ratings. Self-evaluation can provide an additional outcome measure and allow patients to be more engaged in their treatment. The Self-evaluation of Negative Symptoms (SNS) has been developed recently. This is a remarkably understandable instrument for patients with schizophrenia as it allows them to readily complete it without assistance, providing information with respect to their own perception of negative symptoms. The SNS is a self-assessment that permits patients to evaluate themselves in 5 dimensions of negative symptoms. This validation study for the SNS revealed good psychometric properties alongside satisfactory acceptance by patients. AimThis study was to confirm the validation of the French version of the self-evaluation of negative symptoms (SNS). MethodsPatients with schizophrenia or schizoaffective disorder according to the DSM-IV-R, with a stable regimen of anti-psychotic drugs for the last two months, aged more than 18 years old were eligible for the study. Symptoms were rated using the SNS, the Scale for the Assessment of Negative Symptoms (SANS), the Calgary Depression Scale for Schizophrenics (CDSS), the Brief Psychiatric Rating Scale (BPRS) and the Clinical Global Impression and Parkinsonism. Patients were asked to fulfill the SNS twice, 6 weeks apart. ResultsSixty patients were evaluated. Cronbach's coefficient (α=0.8) showed good internal consistency. The SNS significantly correlated with the SANS (r=0.6), the negative sub-score of the BPRS (r=0.6) and the Clinician Global Impression on the severity of negative symptoms (r=0.7). SNS scores did not correlate with level of insight (r=0.08) or Brief Psychiatric Rating Scale positive sub-scores (r=0.2). SNS scores correlated with CDSS scores. However, we did not find correlation between the first item of the CDSS which evaluates depression and the “diminished emotional range” sub-score of SNS. The test-retest of SNS revealed no changes of scores at two evaluations 6 weeks apart. ConclusionThe acceptance by patients of the SNS was excellent. The French version of the SNS demonstrated a good internal consistency, good convergent validity and good discriminant validity. The study demonstrates the ability of patients with schizophrenia to accurately report their own experiences. Self-assessments of negative symptoms should be more widely employed in clinical practice because they may allow patients with schizophrenia to develop appropriate coping strategies.