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

Figures & data

Table 1 Characteristics of the NARCOMS and DER-401 cohorts

Characteristic	NARCOMS cohort^Citation8 (n=3,505)	DER-401 study^Citation9
		Baseline (n=429)	Week 4 (n=398)
Age, mean (SD)	56.7 (10.0)	52.6 (9.5)	52.6 (9.5)
Female,%	80.7	69.9	70.4
MSWS-12 score, mean (SD)
Total score	50.8 (33.5)	62.4 (24.2)	53.0 (25.8)
Item 1	2.67 (1.39)	3.12 (1.03)	2.88 (1.07)
Item 2	3.86 (1.57)	4.33 (1.24)	4.18 (1.28)
Item 3	2.91 (1.44)	3.42 (1.12)	3.20 (1.17)
Item 4	2.68 (1.38)	3.07 (1.09)	2.81 (1.12)
Item 5	2.86 (1.35)	3.36 (1.08)	3.01 (1.10)
Item 6	3.23 (1.49)	3.65 (1.12)	3.23 (1.18)
Item 7	3.04 (1.46)	3.39 (1.17)	2.96 (1.18)
Item 8	2.63 (1.61)	3.28 (1.39)	2.87 (1.39)
Item 9	2.81 (1.72)	3.38 (1.51)	3.03 (1.46)
Item 10	3.23 (1.50)	3.52 (1.19)	2.95 (1.26)
Item 11	3.26 (1.49)	3.66 (1.11)	3.10 (1.19)
Item 12	3.29 (1.49)	3.78 (1.20)	3.21 (1.25)
EQ-5D-3L, mean (SD)	0.74 (0.18)	0.70 (0.17)	0.73 (0.15)

Abbreviations: NARCOMS, North American Research Committee on Multiple Sclerosis; DER, dalfampridine extended release; EQ-5D-3L, EuroQol 5-dimension 3-level version; MSWS-12, 12-item Multiple Sclerosis Walking Scale; SD, standard deviation.

Table 2 Precision of the NARCOMS ordinary least squares mapping equation applied to data from study DER-401a

Model	MAE (SD)	RMSE
NARCOMS cohort^Citation8
Overall EQ-5D-3L (n=3,505)	0.109 (0.096)	0.145
EQ-5D-3L <0.50 (n=438; 12.5%)	0.297 (0.094)	0.312
EQ-5D-3L 0.50–<0.75 (n=867; 24.7%)	0.063 (0.054)	0.083
EQ-5D-3L ≥0.75 (n=2,200; 62.8%)	0.089 (0.060)	0.107
DER-401 at baseline^Citation9
Overall EQ-5D-3L (n=429)	0.116 (0.103)	0.155
EQ-5D-3L <0.50 (n=59; 13.8%)	0.313 (0.098)	0.328
EQ-5D-3L 0.50–<0.75 (n=147; 34.3%)	0.063 (0.048)	0.080
EQ-5D-3L ≥0.75 (n=223; 51.9%)	0.099 (0.062)	0.116
DER-401 at week 4^9
Overall EQ-5D-3L (n=398)	0.105 (0.090)	0.138
EQ-5D-3L <0.50 (n=40; 10.0%)	0.295 (0.080)	0.305
EQ-5D-3L 0.50–<0.75 (n=136; 34.2%)	0.081 (0.065)	0.104
EQ-5D-3L ≥0.75 (n=222; 55.8%)	0.085 (0.058)	0.104

Notes:

a Mapping model is EQ-5D-3L =+0.002× (item 1), −0.009× (item 2), −0.01× (item 3), −0.029× (item 4), −0.019× (item 5), −0.0000881× (item 6), −0.008× (item 7), −0.002× (item 8), +0.013× (item 9), −0.011× (item 10), +0.001× (item 11), −0.008× (item 12), and +0.983 (constant).

Abbreviations: NARCOMS, North American Research Committee on Multiple Sclerosis; DER, dalfampridine extended release; EQ-5D-3L, EuroQol 5-dimension 3-level version; MAE, mean absolute error; RMSE, root-mean-square error; SD, standard deviation.

Table 3 Percentage of predicted EQ-5D-3L values within ranges of absolute error of observed value in DER-401 relative to data from the original validation study

Absolute error	EQ-5D-3L estimates
	NARCOMS cohort^Citation8	DER-401 study^Citation9
		Baseline	Week 4
≤0.01	6.5%	4.3%	8.3%
0.01< error ≤0.03	12.5%	13.1%	9.1%
0.03< error ≤0.05	11.0%	13.4%	13.9%
0.05< error ≤0.07	11.5%	11.1%	12.3%
0.07< error ≤0.10	19.4%	14.4%	15.1%
0.10< error ≤0.12	7.4%	4.0%	8.6%
>0.12	31.8%	39.8%	32.8%

Abbreviations: NARCOMS, North American Research Committee on Multiple Sclerosis; DER, dalfampridine extended release; EQ-5D-3L, EuroQol 5-dimension 3-level version.

Figure 1 Scatterplot of observed versus predicted EQ-5D-3L scores for the DER-401 cohort at baseline.

Note: Data points lying closest to the diagonal line (representing the line of perfect fit) illustrate more precise estimates of observed EQ-5D-3L scores.
Abbreviations: DER, dalfampridine extended release; EQ-5D-3L, EuroQol 5-dimension 3-level version.

Figure 2 Scatterplot of observed versus predicted EQ-5D-3L scores for the DER-401 cohort at week 4.

Note: Data points lying closest to the diagonal line (representing the line of perfect fit) illustrate more precise estimates of observed EQ-5D-3L scores.
Abbreviations: DER, dalfampridine extended release; EQ-5D-3L, EuroQol 5-dimension 3-level version.

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.□

In the past two weeks, how much has your MS …	Not at all	A little	Moderately	Quite a bit	Extremely
1. Limited your ability to walk?	1	2	3	4	5
2. Limited your ability to run?	1	2	3	4	5
3. Limited your ability to climb up and down stairs?	1	2	3	4	5
4. Made standing when doing things more difficult?	1	2	3	4	5
5. Limited your balance when standing or walking?	1	2	3	4	5
6. Limited how far you are able to walk?	1	2	3	4	5
7. Increased the effort needed for you to walk?	1	2	3	4	5
8. Made it necessary for you to use support when walking indoors (eg, holding on to furniture, using a stick, etc.)?	1	2	3	4	5
9. Made it necessary for you to use support when walking outdoors (eg, using a stick, a frame, etc.)?	1	2	3	4	5
10. Slowed down your walking?	1	2	3	4	5
11. Affected how smoothly you walk?	1	2	3	4	5
12. Made you concentrate on your walking?	1	2	3	4	5

Please check that you have circled ONE number for EACH question

Note: Reprinted with permission from Hobart JC, Riazi A, Lamping DL, Fitzpatrick R, Thompson AJ. Measuring the impact of MS on walking ability: the 12-item MS Walking Scale (MSWS-12). Neurology. 2003;60(1):31–36.¹ Promotional and commercial use of the material in print, digital or mobile device format is prohibited without the permission from the publisher Wolters Kluwer Health. Please contact [e-mail] for further information.

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