Constructing an Index for the Subjective Well-being Under Neuroleptics Scale (SWN), short form: Applying structural equation modeling for testing reliability and validity of the index

Abstract

Structural equation modeling (SEM) has been widely used in psychology and sociology for testing validity of measurement instruments. However, this statistical technique has so far played minor role in quality-of-life research. The main objective of this paper is to demonstrate the potential of SEM for constructing and testing the validity of a Subjective Well-being under Neuroleptics (SWN) index for patients with schizophrenia. For these purposes, data from the GEO study (Gesundheitsökonomische Evaluation von Olanzapin in Deutschland; Health economics study of olanzapine in the treatment of schizophrenia in Germany) were used. The GEO is a prospective, comparative, noninterventional, observational study. A total of 646 participants treated with either olanzapine (n = 416) or haloperidol (n = 230) were enrolled in the study; 360 patients were available for factor analyses. The short (20-item) form of the SWN scale was administered to assess patients' perspectives on their quality of life. The structural equation models (SEMs) were then applied to construct 5- and 10-item indexes based on SWN. The data indicate that the 5-item index is the most time-saving approach for evaluating perceptions of well-being (and thus, quality of life) among patients with schizophrenia. The application of SEM showed no appreciable loss of validity of this index.