Can we derive an 'exchange rate' between descriptive and preference-based outcome measures for stroke? Results from the transfer to utility (TTU) technique

Table 3 Post-sample predictive validity for 'all stroke' SF-36 to AQoL algorithms

Data	Model	Group	N	Min	Max	Mean	SD
Observed AQoL	Validation sample	NIHSS = 0	786	-0.04	1.00	0.529	0.334
		NIHSS = 1–5	337	-0.04	1.00	0.440	0.296
		NIHSS ≥ 6	114	-0.04	1.00	0.112	0.205
		Missing	19	-0.03	1.00	0.278	0.357
		Total	1256	-0.04	1.00	0.464	0.337
Predicted AQoL	Scale-based	NIHSS = 0	580	0.20	0.75	0.494	0.134
		NIHSS = 1–5	334	0.21	0.73	0.450	0.123
		NIHSS ≥ 6	112	0.22	0.66	0.361	0.097
		Missing	19	0.25	0.73	0.403	0.141
		Total	1045	0.20	0.75	0.464	0.134
	Subscale-based	NIHSS = 0	580	0.10	0.79	0.523	0.193
		NIHSS = 1–5	334	0.12	0.80	0.456	0.185
		NIHSS ≥ 6	112	0.10	0.73	0.262	0.144
		Missing	19	0.10	0.73	0.346	0.206
		Total	1045	0.10	0.80	0.460	0.202
	Item-based	NIHSS = 0	581	0.05	0.80	0.513	0.191
		NIHSS = 1–5	335	-0.01	0.78	0.453	0.185
		NIHSS ≥ 6	112	0.02	0.72	0.262	0.150
		Missing	19	0.11	0.77	0.363	0.215
		Total	1047	-0.01	0.80	0.464	0.200
Mean Absolute Deviation (MAD)	Scale-based	NIHSS = 0	580	0.00	0.54	0.215	0.120
		NIHSS = 1–5	334	0.00	0.62	0.196	0.123
		NIHSS ≥ 6	112	0.01	0.49	0.280	0.097
		Missing	19	0.03	0.45	0.246	0.132
		Total	1045	0.00	0.62	0.216	0.121
	Subscale-based	NIHSS = 0	580	0.00	0.77	0.164	0.109
		NIHSS = 1–5	334	0.00	0.62	0.161	0.117
		NIHSS ≥ 6	112	0.01	0.56	0.184	0.103
		Missing	19	0.04	0.33	0.176	0.080
		Total	1045	0.00	0.77	0.165	0.111
	Item-based	NIHSS = 0	581	0.00	0.65	0.163	0.109
		NIHSS = 1–5	335	0.00	0.68	0.181	0.117
		NIHSS ≥ 6	112	0.01	0.68	0.181	0.117
		Missing	19	0.03	0.36	0.175	0.102
		Total	1047	0.00	0.68	0.163	0.111

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