Examining the Factor Structure and Psychometric Properties of the Quality of Life Scale Among People With Multiple Sclerosis

Abstract

Rehabilitation counseling researchers seeking to more fully understand the phenomenon of psychosocial adaptation to disability are devoting increased attention to the impact of disability on quality of life (QOL). This impact has been of particular interest among multiple sclerosis (MS) researchers. The complex etiology, unpredictable nature, and the multiple functional limitations attendant to MS have been identified as major impediments in research efforts to develop psychometrically sound and clinically sensitive tools to evaluate the impact of MS on QOL. This article presents the results of a confirmatory factor analysis of the factor structure of the Quality of Life Scale (QOLS), which has been used in several studies to evaluate the impact of MS on QOL. The QOLS was developed to assess the self-reported QOL of people with chronic pain and evaluates the degree of satisfaction with 7 distinct domains of personal and social activity. The developers’ original principal component analysis revealed a single-factor model with high levels of internal consistency reliability. It is not clear, however, how the 1-factor model fits the population of individuals with MS and how the 7 items perform in terms of their measurement of the single factor. The 1-factor structure of the QOLS did not fit the data well in this sample of individuals with MS. Subsequent model iterations that incorporated 3 error covariances provided increasingly better fit and resulted in a reasonable model fit to the data.