Confirmatory factor analysis of the quality of life scale and new proposed factor structure for the quality of life scale-revised

Abstract

The Quality of Life Scale (QLS) is a frequently used semistructured interview for the assessment of functional outcomes in schizophrenia. Despite the use of the QLS for over 30years, the original 4-factor structure of the instrument (Interpersonal Relations, Instrumental Role, Intrapsychic Foundations, and Common Objects and Activities) has not been rigorously examined. Exploratory factor analyses (EFAs) and confirmatory factor analyses (CFAs) were used to evaluate the factor structure of the QLS in two independent datasets, including a mixed diagnostic sample of multi-episode participants (N=247), and a sample of individuals with a first episode of psychosis (N=337). A CFA with the first dataset indicated a poor fit for the 4-factor model of the QLS. Subsequent EFAs on this dataset led to a more promising 3-factor solution including 16/21 of the QLS items, which were similar to the first 3 of 4 factors originally proposed for the QLS. CFAs on the same dataset indicated that the 3-factor model for the QLS-Revised (QLS-R) fit the data well. This factor structure was evaluated with the second dataset using CFA and was also found to be fit the data well. The results support the robustness of the 3-factor model of the QLS-R in schizophrenia and mixed diagnostic samples. Future research should evaluate the validity of the 3-factor model of the QLS-R, and consider the merits of changing the name of the Intrapsychic Foundations factor to Motivation.