The use of multiple sclerosis condition-specific measures to inform health policy decision-making: mapping from the MSWS-12 to the EQ-5D

Background: Walking impairment has a major influence on the quality of life of people with multiple sclerosis (MS). The Multiple Sclerosis Walking Scale (MSWS-12) assesses the impact of MS on walking ability from the patient's perspective, but in its current form, is not amenable for use in many policy decision-making settings. Objectives: Statistical 'mapping' methods were used to convert MSWS-12 scores to EQ-5D health state values. Methods: The relationship between the measures was estimated using cohort data from people with MS in South West England. Regression analyses were conducted, estimation errors assessed, and predictive performance of the best models tested using longitudinal data. Results: Model performance was in line with that of other mapping studies, with the best-performing models being an ordinary least squares (OLS) model using MSWS-12 item scores, and an OLS model using the total MSWS-12 score and its squared term. Conclusions: A process has been described whereby data from a patient-reported outcome measure (MSWS-12) can be converted to (EQ-5D) health state values. These values may be used to consider the health-related quality of life of people with MS, to estimate quality adjusted life-years for use in effectiveness and cost-effectiveness analyses, and to inform health policy decisions.