Background: To monitor the unique side effect pattern of clozapine, the Glasgow Antipsychotic Side-effect Scale for Clozapine (GASS-C) was developed in English and validated. This questionnaire was previously translated to Dutch, and revised, but not yet validated.
Aim: The current study concerns the validation of the second revision of the GASS-C-NL-R2 for the Dutch language.
Method: Two Spearman correlation tests were conducted to compare GASS-C-NL-R2 with the Dutch version of the Liverpool University Neuroleptic Side-Effect Rating Scale (LUNSERS) at two time p´oints. There was one week between these two time points. The test-retest reliability was determined using a Spearman correlation test and Cronbach's alpha on the GASS-C-NL-R2 between the two time points. In addition, a factor analysis was performed.
Results: Spearman's correlation coefficient between the GASS-C-NL-R2 and the LUNSERS was 0.830 (p < 0.001, n = 72) at the first time point and 0.684 (p < 0.001, n = 50) at the second time point. GASS-C-NL-R2 also had a strong test-retest reliability: Spearman's correlation coefficient was 0.680 (p < 0.001; n = 46), and Cronbach's alpha was 0.847, n = 78. Factor analysis showed that all questions were relevant.
Conclusion: The current study shows that GASS-C-NL-R2 is a valid and reliable questionnaire to monitor side effects related to clozapine with a relatively high prevalence. Future studies should focus on the practical utility of GASS-C-NL-R2 with a larger sample size.