Validity and reliability evaluation of Chinese version of Glasgow antipscyhotics side-effect scale based on the experience of schizophrenia patients

Objective To evaluate the reliability and validity of Chinese version of Glasgow antipsychotics side-effect scale (GASS). Methods Totally 200 patients diagnosed as schizophrenia following the criteria of DSM-IV were enrolled in the study.Cronbach’s α was used to investigate the internal consistency of GASS.Exploring factor analysis was used to examine the construct validity.Pearson correlation analysis between GASS and TESS and CGI sub-scale of side effect were conducted to evaluate the criterion validity.Based on clinical criteria, the sensitivity and specificity and ROC curve was calculated so as to establish the cut-off point of the scale and test discrimination validity. Results For reliability, Cronbach’s α ws 0.926, indicating that GASS had a good internal consistency.Four main factors were extracted by exploratory factor analysis which were extrapyramidal side effect factor, genitourinary side effect factor, anticholinergic side effect factor, over sedation and cardiovascular side effect factor.For validity, exploring analysis demonstrated that nineteen item of the scale has relatively higher factor load on the principal factor (0.531-0.972), suggesting that the scale had a good construct validity.The total score of the GASS was positively correlated with that of TESS and CGI subscale of side effects(r=0.90, P<0.05; r=0.87, P<0.05). The cut-off point of experimental validity of GASS for mild antipsychotics side effects was determined as ≥1.With this cut-off point, GASS had both high sensitivity (96.3%) and high specificity (70.7%), area under curve (AUC) were 0.78.The cut-off point of GASS for moderate antipsychotics side effects was determined as ≥20, with the sensitivity and specificity of GASS were 86.3% and 84.7%, AUC were 0.92.When the cut-off point of GASS for severe antipsychotics side effects was determined as ≥41, GASS had both high sensitivity (92.1 %) and high specificity (96.3 %), AUC were 0.96. Conclusion GASS has good reliability and validity and can reflect the side effects of antipsychotics, and it can be adopted as a useful instrument to evaluate the severity of side effects of antipsychotics. Key words: Atypical antipsychotics; Side-effect; Rating scale; Validity; Reliability