A Turkish Validity and Reliability Study of the Swiss Narcolepsy Scale

Background: The clinical evaluation of a patient complaining of excessive daytime sleepiness is of crucial importance for the diagnosis of narcolepsy. The Swiss Narcolepsy Scale (SNS) was developed in 2004 as a screening tool for patients with narcolepsy and shown in three different studies to have a high sensitivity and specificity for narcolepsy type 1 (NT1). The aim of this study was to assess the validity and reliability of the Turkish version of SNS (SNS-TR). Patients and Methods: Twenty-one healthy controls, 26 patients with idiopathic hypersomnia, and 27 patients with narcolepsy were recruited from five accredited sleep centers in Turkey. Pearson’s correlation coefficient and degree of freedom were used to determine the validity of each question. Cronbach’s alpha was calculated to assess the internal consistency or reliability of Likert-type questions. The inter-rater reliability was tested using Cohen’s kappa analysis, and the intra-class correlation coefficient (ICC) was used to evaluate the validity and reliability between two evaluations with a one-month interval. Results: Sensitivity and specificity of SNS-TR were 90.5% and 100%, respectively, for diagnosing NT1. Cronbach’s alpha was 0.976, showing a highly reliable level of internal consistency. The inter-rater reliability of the questions and the validity and reliability between two evaluations were moderate or above. Conclusion: This study provides evidence for the validity and reliability of SNS-TR in diagnosing and discriminating NT1 from other disorders of hypersomnolence with a very high sensitivity and specificity.