Reliability of the Glasgow Antipsychotic Side-effects Scale for Clozapine Japanese version (GASS-C-J)

PLoS One. 2020 Jun 18;15(6):e0234864. doi: 10.1371/journal.pone.0234864. eCollection 2020.


The purpose of this study was to develop the Glasgow Antipsychotic Side effects Scale for Clozapine Japanese version (GASS-C-J) and examine its reliability to assess clozapine-related side effects. We developed the GASS-C-J using forward and backward translation. Semantic equivalence of the GASS-C-J to the GASS-C was confirmed by the original author. We then administered the GASS-C-J twice to 109 patients on clozapine treatment at two psychiatric hospitals in Japan. We assessed the internal consistency and test-retest reliability of the GASS-C-J using Cronbach's alpha and weighted kappa coefficient, respectively. We also examined if discrepancies in each GASS-C-J item score between the first and second rating were correlated with items of the Brief Evaluation of Psychosis Symptom Domains (BE-PSD). The Cronbach's alpha coefficient of the GASS-C-J at the first and second rating was 0.78 (95% CI: 0.72 to 0.84) and 0.82 (95% CI: 0.76 to 0.88), respectively. The weighted kappa coefficient of individual and total GASS-C-J item scores ranged from 0.45 to 0.88. Some symptom domains were correlated with discrepancies in specific items of the GASS-C-J: psychotic symptoms and nausea/vomiting (rs = 0.27), thirst (rs = 0.31), and appetite/weight gain (rs = 0.27); disorganized thinking and urinary incontinence (rs = 0.26); depression/anxiety and myoclonus (rs = 0.25), hypersalivation (rs = -0.27), and blurred vision (rs = -0.22). These findings demonstrate that the GASS-C-J can be used in clinical and research settings as a reliable scale to assess clozapine-related side effects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antipsychotic Agents / adverse effects*
  • Antipsychotic Agents / blood
  • Antipsychotic Agents / therapeutic use
  • Clozapine / adverse effects*
  • Clozapine / blood
  • Clozapine / therapeutic use
  • Cross-Sectional Studies
  • Drug Resistance / drug effects
  • Female
  • Glasgow Outcome Scale / standards*
  • Hospitals, Psychiatric
  • Humans
  • Japan
  • Male
  • Middle Aged
  • Psychometrics / methods
  • Reproducibility of Results
  • Schizophrenia / drug therapy*
  • Surveys and Questionnaires


  • Antipsychotic Agents
  • Clozapine

Grant support

This research was supported by a grant from Kobayashi Magobe Memorial Medical Foundation to RS and Inokashira Hospital to NN. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.