Structural and construct validity of the Leeds Multiple Sclerosis Quality of Life scale

Abstract

Purpose: The Leeds Multiple Sclerosis Quality of Life (LMSQOL) scale was designed as an 8-item, unidimensional disease-targeted measure of quality of life (QOL). This study (1) tested the unidimensionality of the LMSQOL using confirmatory factor analysis (CFA) and (2) examined the construct validity of scores based on a nomological network.

Methods: The sample (N = 292) included persons with multiple sclerosis (MS) who were recruited from the Midwest region of the USA. Participants completed questionnaires that were delivered and returned using US Postal Service. We tested the fit of a single-factor model for the LMSQOL using CFA with the diagonally weighted least squares estimator in R. We examined the construct validity of the LMSQOL scores using Spearman rank-order correlations (r s) in SPSS.

Results: The single-factor model had a reasonable fit for the 8-item LMSQOL [χ (2) (20) = 83.19, p < .001, CFI = .97, SRMR = .07], but provided an excellent fit for a 7-item version of the LMSQOL [χ (2) (14) = 23.63, p > .05, CFI = .99, SRMR = .05]. LMSQOL scores demonstrated strong correlations with measures of psychological well-being (|r s| = .53-.74) and weak-to-moderate correlations with measures of physical functioning and disability (|r s| = .23-.57).

Conclusion: The unidimensional model provides a good fit for the LMSQOL, and its scores provide a valid measure of QOL in MS.

Keywords: Construct validity; Factor analysis; Multiple sclerosis; Quality of life; Well-being.