The WHOQOL-BREF: a modern psychometric evaluation of its internal construct validity in people with multiple sclerosis.

ABSTRACT

PURPOSE: Symptoms of Multiple Sclerosis (MS) differentially impact upon quality of life (QoL) and a comprehensive measure is required for use in observational and interventional studies. This study examines the abbreviated World Health Organisation Quality of Life tool (WHOQOL-BREF) which was designed to be used as a broad measure of QoL across different cultures and diseases. METHODS: Data were collected from 3186 subjects as part of the TONiC study in MS and was examined with a systematic, iterative approach using Rasch analysis to investigate the internal construct validity of the WHOQOL-BREF. RESULTS: Mean age was 49.8 years (SD 11.8), disease duration was 11.2 years (SD 9.6) and 73.2% were female. Subjects represented all stages of MS with EDSS scores of 0-4, 4.5-6.5, 7-7.5 and ≥ 8 seen in 49.8%, 38.5%, 6.8% and 4.9% of patients, respectively. Using a super-item approach, it was possible to demonstrate fit to the assumptions of the Rasch model for 3 of the 4 domains of the WHOQOL-BREF (physical, psychological and environment) as well as a broad 24-item total score. In addition, item subsets derived from the stem of each question were shown to function as novel scales measuring impact and life satisfaction. We have provided transformation tables from ordinal raw scores to interval scales where data are complete. CONCLUSIONS: The validation of multiple conceptual frameworks validates the WHOQOL-BREF as a powerful and flexible end-point for use in clinical trials and in testing conceptual models of factors influencing QoL in MS.