Refinement of the SWN-20 based on the Rasch rating model

Objectives The aim of the present study was to refine the 20-item Subjective Well-Being under Neuroleptic Treatment Scale (SWN-20) using the Rasch rating model to validate measurements of subjective well-being in patients with schizophrenia undergoing antipsychotic treatment. Methods In total, 854 (403 males, 451 females) inpatients (n = 213) and outpatients (n = 641) with schizophrenia participated in this study, which was designed as an open-label investigation of paliperidone extended release. The participants completed the Korean version of the SWN-20 themselves. Refinement of the Korean version of the SWN-20 was accomplished using the Rasch rating model. Results Infit and outfit statistics for all 20 items satisfied the criterion for construct validity. Second, all items except items 2 and 20 had suitable point-measure correlations, reflecting content validity. Third, item characteristic curves indicated that roughly 18 items were evenly distributed along the person ability continuum. Finally, option analysis of the category characteristics showed that categories 3 and 4 in the SWN-20 response format were unnecessary. Conclusions We offer several recommendations for improving the SWN-20: (a) items 2 and 20 should be omitted to ensure construct validity; (b) easier items would be added related to the person ability estimates in the process of validating a short form of the SWN scale based on item response theory; and (c) the number of response categories should be reduced for schizophrenic patients.