Psychometric Properties of Quality of Life and Health-Related Quality of Life Assessments in People with Multiple Sclerosis

Background: There is substantial interest in testing interventions for improving quality of life (QOL) and health-related quality of life (HRQOL) in people with multiple sclerosis (MS). Yet, there is limited research on the psychometric properties of QOL (e.g., Satisfaction With Life Scale (SWLS), Leeds MS Quality of Life Scale (LMSQOL)) and HRQOL (e.g., Short-form 12 Health Survey (SF-12) and Multiple Sclerosis Impact Scale-29 (MSIS-29)) measures in this population. Such research is important for designing and interpreting interventions. 

Objectives: We examined the test-retest reliability, measurement error, and interpretability of QOL (i.e., SWLS and LMSQOL) and HRQOL (i.e., SF-12 and MSIS-29) measures over six months in people with MS.

Methods: Individuals with MS (N = 274) completed the SWLS, LMSQOL, SF-12 and MSIS-29 on two occasions, six-months apart. We estimated test re-test reliability (Intraclass Correlation Coefficient (ICC)), measurement error (Standard Error of Measurement (SEM) and Coefficient of Variation (CV)) and interpretability (Smallest Detectable Change (SDC)). 

Results: ICC values ranged between moderate and good (ICC range = .669 - .883); the LMSQOL had the best reliability and the SF-12 the worst reliability. Measurement error varied amongst measures (e.g., SEM % range = 10.9 – 30.7); the LMSQOL had the best measurement error and the MSIS-29 the worst measurement error.  Interpretability varied amongst measures (SDC % range 30.1 – 89.0); interpretability was best for the LMSQOL and worst for the MSIS-29.

Conclusions: We provide novel data for helping researchers and clinicians select and interpret QOL and HRQOL measures and scores for interventions among people with MS. Such information will better inform our understanding of intervention effectiveness.