Psychometric properties and diagnostic criteria of Scale for the assessment of negative symptoms (SANS) in schizophrenia

The Scale for the assessment of negative symptoms (SANS) is one of the most widely used clinical assessment tools for negative symptoms.

The purpose of this study was psychometric analysis and modification of the SANS with the definition of criteria for assessing the severity of negative symptoms in the dynamics of therapy in patients with schizophrenia.

Material and methods: The study involved 157 patients with a diagnosis of schizophrenia, the age range of participants ranged from 18 to 59 years. Psychometric analysis was done on the base of the Rush measurement with the definition of criteria for assessing the severity of negative symptoms based on the index of minimum detectable changes for 95% probability (Minimum detectable change95%— MDC95%).

Results: Five SANS diagnostic items with low construct validity were identified. The technique was modified by excluding these invalid items. SANS was modified by eliminating of 5 invalid items. The modified version of SANS demonstrated high reliability (reliability index = 0.97) and discriminativeness (the ability to differentiate 12 metric levels of severity of negative symptoms). Factor analysis revealed the heterogeneity of the metric structure of the technique: points in the first group reflect the impoverishment of speech and emotional manifestations, points in the second group reflect the decrease of the patient’s involvement in various activities and restriction of social interaction. Thus, the two-dimensional structure of the SANS scale (“expression” factor and “motivation” factor) is fully consistent with the modern concept of negative symptoms, which allows to consider the total SANS score as an indicator of the severity of the negative syndrome construct. In the course of the metric analysis, the criteria for assessing the severity of negative symptoms in the dynamics of the therapy were determined.

Conclusion: The modified version of SANS has adequate psychometric characteristics. The diagnostic criteria are suitable for use in clinical practice and research.

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