Mapping of Multiple Sclerosis Walking Scale (MSWS-12) to five-dimension EuroQol (EQ-5D) health outcomes: an independent validation in a randomized control cohort

Abstract

Background

Mapping of patient-reported outcomes to the five-dimension EuroQol (EQ-5D) health index is increasingly being used for understanding the relationship of outcomes to health states and for predicting utilities that have application in economic evaluations. The 12-item Multiple Sclerosis Walking Scale (MSWS-12) is a patient-reported outcome that assesses the impact of walking impairment in people with MS. An equation for mapping the MSWS-12 to the EQ-5D was previously developed and validated using a North American Research Committee on MS (NARCOMS) registry cohort.

Materials and methods

This analysis retested the validity of the equation mapping the MSWS-12 to the three-level EQ-5D (EQ-5D-3L) by using an independent cohort of patients with MS enrolled in a randomized controlled trial. Mapping was evaluated at two separate time points (baseline and week 4) during the clinical trial. The mapping equation’s performance was subsequently assessed with mean absolute error (MAE) and root-mean-square error (RMSE) by comparing equation-based estimates to values elicited in the trial using the actual EQ-5D-3L questionnaire.

Results

The mapping equation predicted EQ-5D-3L values in this external cohort with reasonable precision at both time points (MAE 0.116 and RMSE 0.155 at baseline; MAE 0.105 and RMSE 0.138 at week 4), and was similar to that reported in the original NARCOMS cohort (MAE 0.109 and RMSE 0.145). Also as observed in the original NARCOMS cohort, the mapping equation performed best in patients with EQ-5D-3L values between 0.50 and 0.75, and poorly in patients with values <0.50.

Conclusion

The mapping equation performed similarly in this external cohort as in the original derivation cohort, including a poorer performance in MS patients with more severe health-state severity.

Keywords:

• health status index
• health-related quality of life
• mapping
• EQ-5D-3L
• MSWS-12

Supplementary material

Table S1 The 12-item Multiple Sclerosis Walking Scale (MSWS-12)

• These questions ask about limitations to your walking due to MS during the past 2 weeks.

• For each statement, please circle the one number that best describes your degree of limitation.

• Please answer all questions even if some seem rather similar to others, or seem irrelevant to you.

• If you cannot walk at all, please tick this box.□

References

• HobartJCRiaziALampingDLFitzpatrickRThompsonAJMeasuring the impact of MS on walking ability: the 12-item MS Walking Scale (MSWS-12)Neurology2003601313612525714
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Disclosure

Dr Coleman received a grant from Acorda Therapeutics and fees from Acorda Therapeutics for board membership and consultancy. Dr Sidovar is an employee of Acorda Therapeutics, Inc. and recieves compensation and securities from the firm. The authors have no other conflicts of interest in this work.