[Validity and reliability of Polish adaptation of Yale Global Tic Severity Scale (YGTSS) in a study of Warsaw schoolchildren aged 12-15].

The aim of the study was to assess the reliability and validity of the Polish adaptation of the YGTSS scale in a study screening a population of 1579 schoolchildren for tic disorders. The scale was administered to 60 children with diagnosis of a tic disorder (15 had transient tic disorder; 37 had chronic tic disorder, and 8 had Tourette disorder). Reliability was computed using Cronbach's alpha coefficient and by evaluation of its internal consistency. Theoretical validity of the scale was evaluated using factor analysis. The computed Cronbach's alpha coefficient for the YGTSS scale was 0.73. All items (except phonic tic complexity) highly correlated with their respective subscale scores. Factor analysis of YGTSS revealed two principal components that recombined the items into categories identical to motor and vocal tic subscales. The overall impairment item loading corresponded to motor tic subscale. The YGTSS scale used in a population sample of 12-15 year old schoolchildren has acceptable validity and reliability. Additional study testing psychometric parameters of the scale could be beneficial, involving subjects with Tourette syndrome with wider age range and interrater agreement